Research activity information

• Sep. 2015 日本動物学会, 成茂動物科学振興賞, ミツバチの社会性行動に関する生物学的および数理学的研究：行動誤差の進化的意義の発見

  OKADA RYUICHI

  International academic award


• Jul. 2006 日本比較生理生化学会, 吉田奨励賞, 運動制御における昆虫の脳の基本設計

  OKADA RYUICHI

  International academic award

• Antennal Responses to Volatiles Related to Host Location in the Ambrosia Beetle Platypus quercivorus (Murayama)

  Ryuichi Okada, Yasuto Ito, Michimasa Yamasaki

  The ambrosia beetle Platypus quercivorus (Murayama) is a vector of Japanese oak wilt, a fungal pathogen that causes mass mortality of Fagaceae trees. The male locates and lands on the host tree and releases an aggregation pheromone that attracts both males and females. Thus, aggregation pheromones and host tree volatiles are important chemicals for host location. However, the antennal responses to these volatiles have not yet been examined. To obtain physiological property of P. quercivorus antennae, we electrophysiologically recorded the antennal responses of this beetle to candidate volatiles, including isoprene and other leaf volatiles (1-hexanol, 2-ethyl-1-hexanol, trans-2-hexenal, decanal, and benzaldehyde) of the host trees, as well as quercivorol (aggregation pheromone) and ethanol (widely used for trapping this insect in the field). Electroantennograms (EAGs) exhibited clear dose-dependent responses to the tested volatiles, but antennae did not respond to decanal. Sexual differences in responses were not observed for almost all volatiles. However, the EAGs suggested that the quercivorol and trans-2-hexenal sensitivity of males was higher than that of females. Ethanol elicited a large EAG amplitude in both sexes, but the sensitivity of males or females to ethanol was lower than that to the other volatiles. EAGs showed a very weak response to isoprene only in males, although isoprene is considered a possible attractant for host location. Our study will facilitate to understand the mechanism of the host location ecologically and neurophysiologically.

  SPRINGER, Apr. 2025, JOURNAL OF CHEMICAL ECOLOGY, 51(2) (2), English

  Scientific journal


• A potential evolutionary trap for the extended phenotype of a nematomorph parasite

  Yuna Sawada, Nozomu Sato, Takeshi Osawa, Kazuma Matsumoto, Ming-Chung Chiu, Ryuichi Okada, Midori Sakura, Takuya Sato

  Abstract Human activities introduce new environmental cues to wild organisms, leading to maladaptive behavioral and life history decisions known as the “evolutionary trap.” This trap is thought to be a major conservation concern for free-living organisms. However, it has never been studied in endosymbionts, one of the most successful and diverse life forms on Earth. Here, we examine this trap in the extended phenotype of a parasite that exploits the visual system of hosts to alter host behavior for its benefit. Arboreal mantids infected by nematomorph parasites are drawn to horizontally polarized light, thereby inducing them to enter the water. In this study, we found that the degree of linear polarization (DOP) of reflected light served as a reliable environmental cue for identifying perennial waters, where nematomorphs can survive in their aquatic life stage without drying out. Infected mantids exhibit attraction to horizontally polarized light with higher DOP in behavioral assays and jumped into pools reflecting light with higher DOP in field experiments. The asphalt road reflected horizontally polarized light closely resembling the polarization levels observed in perennial waters, likely leading to a higher prevalence of mantids on asphalt roads compared with those found in natural arboreal habitats. In a field experiment, we observed infected mantids walking on asphalt roads more often than on cement roads. These findings imply that evolutionary traps can endanger endosymbionts beyond their hosts that directly perceive environmental cues.

  Oxford University Press (OUP), Oct. 2024, PNAS Nexus, 3(10) (10)

  [Refereed]

  Scientific journal


• Massive horizontal gene transfer and the evolution of nematomorph-driven behavioral manipulation of mantids

  Tappei Mishina, Ming-Chung Chiu, Yasuyuki Hashiguchi, Sayumi Oishi, Atsunari Sasaki, Ryuichi Okada, Hironobu Uchiyama, Takeshi Sasaki, Midori Sakura, Hirohiko Takeshima, Takuya Sato

  Elsevier BV, Nov. 2023, Current Biology, 33(22) (22), 4988 - 4994.e5

  [Refereed]

  Scientific journal


• Honey Bee Waggle Dance as a Model of Swarm Intelligence

  Ryuichi Okada, Hidetoshi Ikeno, Hitoshi Aonuma, Midori Sakura, Etsuro Ito

  Aug. 2023, Journal of Robotics and Mechatronics

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Visual learning in tethered bees modifies flight orientation and is impaired by epinastine

  Norihiro Kobayashi, Yuji Hasegawa, Ryuichi Okada, Midori Sakura

  Abstract Visual-orientation learning of a tethered flying bee was investigated using a flight simulator and a novel protocol in which orientation preference toward trained visual targets was assessed in tests performed before and after appetitive conditioning. Either a blue or a green rectangle (conditioned stimulus, CS) was associated with 30% sucrose solution (unconditioned stimulus, US), whereas the other rectangle was not paired with US. Bees were tested in a closed-looped flight simulator 5 min after ten pairings of the US and CS. Conditioned bees were preferentially oriented to the CS after such training. This increase in preference for CS was maintained for 24 h, indicating the presence of long-term memory. Because the total orienting time was not altered by conditioning, conditioning did not enhance orientation activity itself but increased the relative time for orientation to CS. When 0.4 or 4 mM epinastine (an antagonist of octopamine receptors) was injected into the bee’s head 30 min prior to the experiment, both short- and long-term memory formation were significantly impaired, suggesting that octopamine, which is crucial for appetitive olfactory learning in insects, is also involved in visual orientation learning.

  Corresponding, Springer Science and Business Media LLC, Mar. 2023, Journal of Comparative Physiology A

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Possible Role of Polarized Light Information in Spatial Recognition in the Cricket Gryllus bimaculatus.

  Nobuaki Matsubara, Ryuichi Okada, Midori Sakura

  Many insects are able to use skylight e-vector patterns to deduce their heading direction. Crickets have been well known to orient themselves to certain e-vector orientations to keep their walking direction. However, it is still unknown if crickets are able to utilize polarized light information for spatial recognition. Using an experimental paradigm similar to the Morris water maze for rodents, here we examine the possibility that the cricket Gryllus bimaculatus can utilize polarized light information to find the target place. Crickets were placed in a round arena with a heated floor, a portion of which was cooled, and a cross-shaped e-vector pattern was presented from the top of the arena so that the cricket could find the cool spot by walking along the e-vector direction. When the arrangement of the e-vector pattern and the cool spot were fixed throughout the experiments, the time and the walking distance to find the cool spot were significantly decreased with increasing trials, but not when the e-vector pattern was rotated between each trial. Moreover, a model selection indicated that the visual stimulus contributed to the decrease in time and distance. To investigate the cricket's exploration patterns in the arena, a test trial in which the whole floor was uniformly heated was performed before and after the training trials. In the test trial, the crickets trained with the positionally fixed e-vector pattern showed wall-following behavior for a significantly longer time than those untrained and those trained with random e-vector patterns.

  Aug. 2021, Zoological science, 38(4) (4), 297 - 304, English, Domestic magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Relationship between the flight distance of ambrosia beetle, Platypus quercivorus and environmental factors

  Fujihara Seima, Ito Yasuto, Pham Duy Long, Okada Ryuichi, Yamasaki Michimasa, Ikeno Hidetoshi

  [in Japanese]

  THE JAPANESE FORESTRY SOCIETY, May 2021, The Japanese Forest Society Congress, 132, 140, Japanese


• Differences between queen piping temporal structures of two honeybee species, Apis cerana and Apis mellifera

  Tetsu Yamamoto, Michio Sugahara, Ryuichi Okada, Hidetoshi Ikeno

  In swarming season, honeybee queens emit two kinds of queen piping signals: tooting and quacking. These signals are considered to be important for swarming, and honeybees distinguish between the two signals through differences in their temporal structures. In this study, we revealed that the piping signals of two honeybee species, Apis cerana and Apis mellifera, had different temporal structures. The tooting of A. cerana consisted of almost one long syllable, while that of A. mellifera was constructed from several syllables. The quacking of both species comprised around 50 short syllables, but the duration and period of the syllables of A. cerana were about half those of A. mellifera. The findings provide new insights that reveal the mechanisms of signal discrimination and the functions of the signals.

  SPRINGER FRANCE, Apr. 2021, APIDOLOGIE, 52(2) (2), 524 - 534, English

  [Refereed]

  Scientific journal


• Females invest more energy in flight: flight characteristics of Platypus quercivorus (Murayama) revealed by a flight mill

  Duy Long Pham, Yasuto Ito, Ryuichi Okada, Hidetoshi Ikeno, Michimasa Yamasaki

  Dispersal flight is an essential component of the life history of bark and ambrosia beetles. Previous studies have shown considerable variation in flight distance between individual beetles; however, different factors drive this variation between species. Furthermore, when the ecological role of dispersal flight differs between sexes (i.e., males locate hosts and females follow), influencing factors might also vary. Here, we evaluated the factors driving variation in the dispersal flight distance of the ambrosia beetle Platypus quercivorus (Murayama) (Coleoptera: Curculionidae: Platypodinae), which is a vector insect of Raffaelea quercivora, the causal agent of the Japanese oak wilt, and we estimated sex-based differences for each influencing factor. A flight mill was used to measure flight distance, flight duration, and initial and terminal flight speed. Because flight speed was not constant during beetle flight, we estimated both initial and terminal flight speed, and assumed that initial flight speed represents a relative measure of energy allocated to flight. Flight distance was mainly determined by flight duration, with an average flight speed of 4.22 km/h for both sexes. Initial and terminal flight speed affected flight distance; however, these factors had contrasting effects between sexes. Specifically, a simultaneous increase in initial and terminal flight speed by males increased flight distance. In comparison, increased flight distance by females was mainly achieved by increasing the initial flight speed. These different patterns in increased flight speed likely reflect differences in the relative importance of flight in the life history of the two sexes.

  2021, Journal of Forest Research, 26(2) (2), 143 - 151

  [Refereed]

  Scientific journal


• Orientation to polarized light in tethered flying honeybees.

  Norihiro Kobayashi, Ryuichi Okada, Midori Sakura

  Many insects exploit the partial plane polarization of skylight for visual compass orientation and/or navigation. In the present study, using a tethering system, we investigated how flying bees respond to polarized light stimuli. The behavioral responses of honeybees (Apis mellifera) to a zenithal polarized light stimulus were observed using a tethered animal in a flight simulator. Flight direction of the bee was recorded by monitoring the horizontal movement of its abdomen, which was strongly anti-correlated with its torque. When the e-vector orientation of the polarized light was rotated clockwise or counterclockwise, the bee responded with periodic right-and-left abdominal movements; however, the bee did not show any clear periodic movement under the static e-vector or depolarized stimulus. The steering frequency of the bee was well coordinated with the e-vector rotation frequency of the stimulus, indicating that the flying bee oriented itself to a certain e-vector orientation, i.e. exhibited polarotaxis. The percentage of bees exhibiting clear polarotaxis was much smaller under the fast stimulus (3.6 deg s-1) compared with that under a slow stimulus (0.9 or 1.8 deg s-1). Bees did not demonstrate any polarotactic behavior after the dorsal rim area of the eyes, which mediates insect polarization vision in general, was bilaterally covered with black paint. Preferred e-vector orientations under the clockwise stimulus varied among individuals and distributed throughout -90 to 90 deg. Some bees showed similar preferred e-vector orientations for clockwise and counterclockwise stimuli whereas others did not. Our results strongly suggest that flying honeybees utilize the e-vector information from the skylight to deduce their heading orientation for navigation.

  Dec. 2020, The Journal of experimental biology, 223(Pt 23) (Pt 23), English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Platypus quercivorus ambrosia beetles use leaf volatiles in host selection

  Duy Long Pham, Yasuto Ito, Ryuichi Okada, Hidetoshi Ikeno, Haruna Kazama, Naoki Mori, Michimasa Yamasaki

  Although chemical volatiles emitted from host and non-host trees have been suggested as important cues for bark and ambrosia beetles, their responses to leaf volatiles is poorly understood. The oak ambrosia beetle, Platypus quercivorus (Murayama) (Coleoptera: Curculionidae), is a vector for the fungus that causes Japanese oak wilt. Using a Y-tube olfactometer, we tested the behavioral response of P. quercivorus to leaf volatiles emitted from four host trees – Quercus crispula Blume, Quercus serrata Murray, Quercus salicina Blume, and Castanea crenata Sieb. & Zucc. (all Fagaceae) – and two non-host trees, Fagus crenata Blume (Fagaceae) and Cryptomeria japonica D. Don (Cupressaceae). A flight mill was used to evaluate the effect of flight on the behavioral response to leaf volatiles. The bioassays were repeated 10× before and 10× after flight in the flight mill for each of the 54 individual beetles. Leaf volatile components were analyzed using gas chromatography–mass spectrometry. The bioassay results supported our hypothesis: P. quercivorus was attracted by the leaf volatiles of hosts and was deterred by the leaf volatiles of non-hosts. The behavioral response of P. quercivorus to the leaf volatiles was stronger after flight. Males had a stronger behavioral response than females to leaf volatiles. The leaf volatile chemical profile of the non-host C. japonica differed from the profile of the host plants. However, the chemical profile of the non-host F. crenata was similar to the profile of the hosts. Our findings provide insight into the functions of leaf chemical volatiles in the interaction of P. quercivorus with its hosts and non-hosts and may help improve the control of P. quercivorus and Japanese oak wilt.

  Dec. 2020, Entomologia Experimentalis et Applicata, 168(12) (12), 928 - 939

  [Refereed]

  Scientific journal


• Effects of leaf conditions and flight activity on the behaviour of Platypus quercivorus (Murayama) (Coleoptera: Platypodidae)

  Duy Long Pham, Yasuto Ito, Ryuichi Okada, Hidetoshi Ikeno, Yuji Isagi, Michimasa Yamasaki

  © 2019 Blackwell Verlag GmbH The important role of semiochemicals in the interactions between plants and insects has been extensively investigated. The volatiles produced by oak trees are thought to attract the ambrosia beetle Platypus quercivorus (Murayama), which causes wilt disease in Quercus trees, resulting in widespread damage. In the present study, we hypothesized that (a) P. quercivorus is attracted to the leaf volatiles emitted by host trees and (b) the response of P. quercivorus to leaf volatiles is affected by flight. An experiment was performed to survey the preferences of both sexes of P. quercivorus for the leaf volatiles of Quercus crispula Blume at various stages of leaf deterioration, represented by different number of days after cutting. Additionally, the effect of flight on both sexes was evaluated by testing the beetle flight on a flight mill. The results showed that P. quercivorus was attracted to the volatiles emitted from fresh leaves and was not attracted to those emitted from dry leaves. This suggests that leaf volatiles from healthy hosts are primary attractants for P. quercivorus. Further, males exhibited increased olfactory responses to leaf volatiles as their flight duration increased, whereas the opposite pattern was observed in females. These results suggest that the different ecological roles of the sexes contribute to differences in olfactory responses.

  Nov. 2019, Journal of Applied Entomology, 143(9) (9), 1000 - 1010

  [Refereed]

  Scientific journal


• Neuroethology of the Waggle Dance: How Followers Interact with the Waggle Dancer and Detect Spatial Information.

  Hiroyuki Ai, Ryuichi Okada, Midori Sakura, Thomas Wachtler, Hidetoshi Ikeno

  Since the honeybee possesses eusociality, advanced learning, memory ability, and information sharing through the use of various pheromones and sophisticated symbol communication (i.e., the "waggle dance"), this remarkable social animal has been one of the model symbolic animals for biological studies, animal ecology, ethology, and neuroethology. Karl von Frisch discovered the meanings of the waggle dance and called the communication a "dance language." Subsequent to this discovery, it has been extensively studied how effectively recruits translate the code in the dance to reach the advertised destination and how the waggle dance information conflicts with the information based on their own foraging experience. The dance followers, mostly foragers, detect and interact with the waggle dancer, and are finally recruited to the food source. In this review, we summarize the current state of knowledge on the neural processing underlying this fascinating behavior.

  Oct. 2019, Insects, 10(10) (10), English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• A Heuristic Trajectory Decision Method to Enhance the Tracking Performance of Multiple Honeybees on a Flat Laboratory Arena

  Kimura Toshifumi, Ohashi Mizue, Crailsheim Karl, Schmickl Thomas, Okada Ryuichi, Radspieler Gerald, Isokawa Teijiro, Ikeno Hidetoshi

  In recent ethological studies, the behaviors and interactions of animals have been recorded by digital video cameras and webcams, which provide high functionality at reasonable cost. However, extracting the behavioral data from these videos is a laborious and time-consuming manual task. We recently proposed a novel method for tracking unmarked multiple honeybees in a flat arena, and developed a prototype software named "K-Track". The K-Track algorithm successfully resolved nearly 90% of cases involving overlapped or interacted insects, but failed when such events happened near an edge of a circular arena, which is commonly employed in experiments. In the present study, we improved our K-Track algorithm by comparing the interaction trajectories obtained from forward and backward playing of video episodes. If the tracking results differed between the forward and backward episodes, the trajectory with lower maximum moving distance per frame is chosen. Based on this concept, we developed a new software, "K-Track-kai", and compared the performances of K-Track and K-Track-kai in honeybee tracking experiments. In the cases of 6 and 16 honeybees, K-Track-kai improved the tracking accuracy from 91.7% to 96.4% and from 94.4% to 96.7%, respectively.

  THE INSTITUTE OF SYSTEMS, CONTROL AND INFORMATION ENGINEERS (ISCIE), 2019, Transactions of the Institute of Systems, Control and Information Engineers, 32(3) (3), 113 - 122, English

  [Refereed]


• Automatic tracking method for multiple honeybees using backward-play movies

  Toshifumi Kimura, Mizue Ohashi, Ryuichi Okada, Karl Crailsheim, Thomas Schmickl, Gerald Radspieler, Teijiro Isokawa, Hidetoshi Ikeno

  © 2017 IEEE. In recent studies, researchers can easily record the behaviors of animals by digital video cameras, which provide high functionality at reasonable cost. However, it is a laborious and time-consuming manual task for them to extract the useful behavioral data from these videos. We recently proposed a tracking method for unmarked multiple honeybees in a flat arena, named the 'K-Track' algorithm. The algorithm can successfully identify and track nearly 90% of interaction cases of targets. In this study, we proposed an improved method for the existing K-Track algorithm by tracking results using backward-play movie. If the tracking results differed between the forward and backward episodes, one of them had probably resulted from correct tracking. Therefore, by comparing the forward and backward trajectories of the same interaction, we assumed that there is the potential for an increase in tracking accuracy. In the experiments, K-Track using backward movies successfully tracked four out of five situations that was failed by original K-Track and we confirmed that the method has the potential of improved tracking accuracy.

  Apr. 2018, 2017 6th International Conference on Informatics, Electronics and Vision and 2017 7th International Symposium in Computational Medical and Health Technology, ICIEV-ISCMHT 2017, 2018-January, 1 - 4

  [Refereed]

  International conference proceedings


• Measuring the flight ability of the ambrosia beetle, Platypus quercivorus (Murayama), using a low-cost, small, and easily constructed flight mill

  OKADA Ryuichi, PHAM Duy Long, ITO Yasuto, YAMASAKI Michimasa, IKENO Hidetoshi

  The ambrosia beetle, Platypus quercivorus (Murayama), is the vector of a fungal pathogen that causes mass mortality of Fagaceae trees (Japanese oak wilt). Therefore, knowing the dispersal capacity may help inform trapping/tree removal efforts to prevent this disease more effectively. In this study, we measured the flight velocity and duration and estimated the flight distance of the beetle using a newly developed flight mill. The flight mill is low cost, small, and constructed using commonly available items. Both the flight mill arm and its vertical axis comprise a thin needle. A beetle specimen is glued to one tip of the arm using instant glue. The other tip is thick due to being covered with plastic, thus it facilitates the detection of rotations of the arm. The revolution of the arm is detected by a photo sensor mounted on an infrared LED, and is indicated by a change in the output voltage when the arm passed above the LED. The photo sensor is connected to a personal computer and the output voltage data are stored at a sampling rate of 1 kHz. By conducting experiments using this flight mill, we found that P. quercivorus can fly at least 27 km. Because our flight mill comprises cheap and small ordinary items, many flight mills can be prepared and used simultaneously in a small laboratory space. This enables experimenters to obtain a sufficient amount of data within a short period.

  2018, Journal of Visualized Experiments, 138(138) (138), e57468, English, International magazine

  [Refereed]

  Scientific journal


• Phototactic behavior of the ambrosia beetle Platypus quercivorus (Murayama) (Coleoptera: Platypodidae) before and after flight

  Duy Long Pham, Yasuto Ito, Ryuichi Okada, Hidetoshi Ikeno, Yuji Isagi, Michimasa Yamasaki

  The ambrosia beetle Platypus quercivorus (Coleoptera: Platypodidae) is a vector of the pathogenic fungi, Raffaelea quercivora (Ophiostomatales: Ophiostomataceae), which causes Japanese oak wilt disease. Previous studies have shown that the beetle displays positive phototactic behavior; however, the adaptive significance of this behavior remains unclear. We postulated that positive phototaxis is necessary to allow the beetle to fly skyward immediately after emergence from a tree, and that this taxis changes following a certain period of flight. The present study aimed to clarify the changes in phototactic behavior of P. quercivorus before and after flight by using individual beetles emerging from the trunk of a Quercus crispula (Fagales: Fagaceae) tree that was attacked in 2014. The response of 60 beetles to light was tested ten times each, before and after flight in a flight mill. A generalized linear mixed model was constructed to predict the probability of positive phototaxis of P. quercivorus before and after flight. A best-fit model showed that the probability of positive phototaxis was lower after flight than before. The results suggest that positive phototaxis of P. quercivorus is decreased after flight.

  SPRINGER/PLENUM PUBLISHERS, May 2017, JOURNAL OF INSECT BEHAVIOR, 30(3) (3), 318 - 330, English

  [Refereed]

  Scientific journal


• Flight ablity of Platypus quercivorus measured by a flight mill

  Fukaya Satoshi, Okada Ryuichi, Itou Yasuto

  [in Japanese]

  THE JAPANESE FORESTRY SOCIETY, 2015, The Japanese Forest Society Congress, 126, 153, Japanese


• Error in the Honeybee Waggle Dance Improves Foraging Flexibility

  Ryuichi Okada, Hidetoshi Ikeno, Toshifumi Kimura, Mizue Ohashi, Hitoshi Aonuma, Etsuro Ito

  The honeybee waggle dance communicates the location of profitable food sources, usually with a certain degree of error in the directional information ranging from 10-15 degrees at the lower margin. We simulated one-day colonial foraging to address the biological significance of information error in the waggle dance. When the error was 30 degrees or larger, the waggle dance was not beneficial. If the error was 15 degrees, the waggle dance was beneficial when the food sources were scarce. When the error was 10 degrees or smaller, the waggle dance was beneficial under all the conditions tested. Our simulation also showed that precise information (0-5 degrees error) yielded great success in finding feeders, but also caused failures at finding new feeders, i.e., a high-risk high-return strategy. The observation that actual bees perform the waggle dance with an error of 10-15 degrees might reflect, at least in part, the maintenance of a successful yet risky foraging trade-off.

  NATURE PUBLISHING GROUP, Feb. 2014, SCIENTIFIC REPORTS, 4, 4175, English

  [Refereed]

  Scientific journal


• What are the elements of motivation for acquisition of conditioned taste aversion?

  Koichi Mita, Akiko Okuta, Ryuichi Okada, Dai Hatakeyama, Emi Otsuka, Miki Yamagishi, Mika Morikawa, Yuki Naganuma, Yutaka Fujito, Varvara Dyakonova, Ken Lukowiak, Etsuro Ito

  The pond snail Lymnaea stagnalis is capable of being classically conditioned to avoid food and to consolidate this aversion into a long-term memory (LTM). Previous studies have shown that the length of food deprivation is important for both the acquisition of taste aversion and its consolidation into LTM, which is referred to as conditioned taste aversion (CTA). Here we tested the hypothesis that the hemolymph glucose concentration is an important factor in the learning and memory of CTA. One-day food deprivation resulted in the best learning and memory, whereas more prolonged food deprivation had diminishing effects. Five-day food deprivation resulted in snails incapable of learning or remembering. During this food deprivation period, the hemolymph glucose concentration decreased. If snails were fed for 2 days following the 5-day food deprivation, their glucose levels increased significantly and they exhibited both learning and memory, but neither learning nor memory was as good as with the 1-day food-deprived snails. Injection of the snails with insulin to reduce glucose levels resulted in better learning and memory. Insulin is also known to cause a long-term enhancement of synaptic transmission between the feeding-related neurons. On the other hand, injection of glucose into 5-day food-deprived snails did not alter their inability to learn and remember. However, if these snails were fed on sucrose for 3 min, they then exhibited learning and memory formation. Our data suggest that hemolymph glucose concentration is an important factor in motivating acquisition of CTA in Lymnaea and that the action of insulin in the brain and the feeding behavior are also important factors. (C) 2013 Elsevier Inc. All rights reserved.

  ACADEMIC PRESS INC ELSEVIER SCIENCE, Jan. 2014, NEUROBIOLOGY OF LEARNING AND MEMORY, 107, 1 - 12, English

  [Refereed]

  Scientific journal


• Development of a New Method to Track Multiple Honey Bees with Complex Behaviors on a Flat Laboratory Arena

  Toshifumi Kimura, Mizue Ohashi, Karl Crailsheim, Thomas Schmickl, Ryuichi Okada, Gerald Radspieler, Hidetoshi Ikeno

  A computer program that tracks animal behavior, thereby revealing various features and mechanisms of social animals, is a powerful tool in ethological research. Because honeybee colonies are populated by thousands of bees, individuals co-exist in high physical densities and are difficult to track unless specifically tagged, which can affect behavior. In addition, honeybees react to light and recordings must be made under special red-light conditions, which the eyes of bees perceive as darkness. The resulting video images are scarcely distinguishable. We have developed a new algorithm, K-Track, for tracking numerous bees in a flat laboratory arena. Our program implements three main processes: (A) The object (bee's) region is detected by simple threshold processing on gray scale images, (B) Individuals are identified by size, shape and spatiotemporal positional changes, and (C) Centers of mass of identified individuals are connected through all movie frames to yield individual behavioral trajectories. The tracking performance of our software was evaluated on movies of mobile multi-artificial agents and of 16 bees walking around a circular arena. K-Track accurately traced the trajectories of both artificial agents and bees. In the latter case, K-track outperformed Ctrax, well-known software for tracking multiple animals. To investigate interaction events in detail, we manually identified five interaction categories; 'crossing', 'touching', 'passing', 'overlapping' and 'waiting', and examined the extent to which the models accurately identified these categories from bee's interactions. All 7 identified failures occurred near a wall at the outer edge of the arena. Finally, K-Track and Ctrax successfully tracked 77 and 60 of 84 recorded interactive events, respectively. K-Track identified multiple bees on a flat surface and tracked their speed changes and encounters with other bees, with good performance.

  PUBLIC LIBRARY SCIENCE, Jan. 2014, PLOS ONE, 9(1) (1), e84656, English

  [Refereed]

  Scientific journal


• Paired pulse ratio analysis of insulin-induced synaptic plasticity in the snail brain

  Jun Murakami, Ryuichi Okada, Yutaka Fujito, Manabu Sakakibara, Ken Lukowiak, Etsuro Ito

  Insulin's action in the brain can directly alter cognitive functioning. We have recently shown that molluscan insulin-related peptides are upregulated following a conditioned taste aversion (CTA) training procedure. In addition, when mammalian insulin is superfused over the isolated Lymnaea stagnalis central nervous system, it elicits long-term synaptic enhancement at the monosynaptic connection between the cerebral giant cell and the buccal 1 (B1) motor neuron. This synaptic enhancement is thought to be a neural correlate of CTA. Here, we examined whether the observed changes in synaptic plasticity were the result of presynaptic and/or postsynaptic alterations using the paired pulse procedure. The paired pulse ratio was unaltered following insulin application, suggesting that insulin's effects on synaptic plasticity are mediated postsynaptically in the B1 motor neuron. Thus, it was suggested that postsynaptic changes need to be considered when insulin's actions on synaptic plasticity are examined.

  COMPANY OF BIOLOGISTS LTD, May 2013, JOURNAL OF EXPERIMENTAL BIOLOGY, 216(10) (10), 1771 - 1773, English

  [Refereed]

  Scientific journal


• Involvement of Insulin-Like Peptide in Long-Term Synaptic Plasticity and Long-Term Memory of the Pond Snail Lymnaea stagnalis

  Jun Murakami, Ryuichi Okada, Hisayo Sadamoto, Suguru Kobayashi, Koichi Mita, Yuki Sakamoto, Miki Yamagishi, Dai Hatakeyama, Emi Otsuka, Akiko Okuta, Hiroshi Sunada, Satoshi Takigami, Manabu Sakakibara, Yutaka Fujito, Masahiko Awaji, Shunsuke Moriyama, Ken Lukowiak, Etsuro Ito

  The pond snail Lymnaea stagnalis is capable of learning taste aversion and consolidating this learning into long-term memory (LTM) that is called conditioned taste aversion (CTA). Previous studies showed that some molluscan insulin-related peptides (MIPs) were upregulated in snails exhibiting CTA. We thus hypothesized that MIPs play an important role in neurons underlying the CTA-LTM consolidation process. To examine this hypothesis, we first observed the distribution of MIP II, a major peptide of MIPs, and MIP receptor and determined the amounts of their mRNAs in the CNS. MIP II was only observed in the light green cells in the cerebral ganglia, but the MIP receptor was distributed throughout the entire CNS, including the buccal ganglia. Next, when we applied exogenous mammalian insulin, secretions from MIP-containing cells or partially purified MIPs, to the isolated CNS, we observed a long-term change in synaptic efficacy (i.e., enhancement) of the synaptic connection between the cerebral giant cell (a key interneuron for CTA) and the B1 motor neuron (a buccal motor neuron). This synaptic enhancement was blocked by application of an insulin receptor antibody to the isolated CNS. Finally, injection of the insulin receptor antibody into the snail before CTA training, while not blocking the acquisition of taste aversion learning, blocked the memory consolidation process; thus, LTM was not observed. These data suggest that MIPs trigger changes in synaptic connectivity that may be correlated with the consolidation of taste aversion learning into CTA-LTM in the Lymnaea CNS.

  SOC NEUROSCIENCE, Jan. 2013, JOURNAL OF NEUROSCIENCE, 33(1) (1), 371 - 383, English

  [Refereed]

  Scientific journal


• Increase in cyclic AMP concentration in a cerebral giant interneuron mimics part of a memory trace for conditioned taste aversion of the pond snail

  Emi Otsuka, Miho Matsunaga, Ryuichi Okada, Miki Yamagishi, Akiko Okuta, Ken Lukowiak, Etsuro Ito

  Conditioned taste aversion (CTA) can be classically conditioned in the pond snail Lymnaea stagnalis and subsequently be consolidated into long-term memory (LTM). The neural trace that subserves CTA-LTM can be summarized as follows: A polysynaptic inhibitory postsyn-aptic potential recorded in the neuron 1 medial (N1M) cell in the conditioned snails as a result of activation of the cerebral giant cell (CGC) is larger and lasts longer than that in control snails. The N1M cell is ultimately activated by the CGC via the neuron 3 tonic (N3t) cell. That is, the inhibitory monosynaptic inputs from the N3t cell to the N1M cell are facilitated. The N1M and N3t cells are the members of feeding central pattern generator, whereas the CGC is a multimodal interneuron thought to play a key role in feeding behavior. Here we examined the involvement of a second messenger, cAMP, in the establishment of the memory trace. We injected cAMP into the CGC and monitored the potentials of the B3 motor neuron activated by the CGC. B3 activity is used as an index for the synaptic inputs from the N3t cell to the N1M cell. We found that the B3 potentials were transiently enlarged. Thus, when the cAMP concentration is increased in the CGC by taste aversion training, cAMP-induced changes may play a key role in the establishment of a memory trace in the N3t cell. © 2013 THE BIOPHYSICAL SOCIETY OF JAPAN.

  2013, Biophysics (Japan), 9, 161 - 166, English

  [Refereed]

  Scientific journal


• Detection of H2O2 by Fluorescence Correlation Spectroscopy

  Etsuro Ito, Satoshi Watabe, Mika Morikawa, Hiromi Kodama, Ryuichi Okada, Toshiaki Miura

  Fluorescence correlation spectroscopy (FCS) is a technique in which measurement of fluorescence intensity fluctuations is used to clarify dynamic molecular interactions within a very small space in a solution containing a small number of fluorescent molecules. The FCS-based analysis gives the average number and average diffusion time of the fluorescent molecules during their passage through a very small space. One advantage of FCS is that physical separation between free and bound fluorescent probes is not required because the properties of fluorescence fluctuations are accounted for. Therefore, when fluorescent probes are bound with proteins by peroxidase and hydrogen peroxide (H2O2), FCS enables us to detect H2O2 with high sensitivity. In addition, because H2O2 is generated by oxidase-catalyzed reactions, a highly sensitive method for detecting H2O2 is applicable to the measurement of low levels of various oxidases and their substrates, such as glucose. We here describe the protocol of a de novo, highly sensitive method for the measurement of H2O2 and glucose using FCS.

  ELSEVIER ACADEMIC PRESS INC, 2013, HYDROGEN PEROXIDE AND CELL SIGNALING, PT A, 526, 135 - 143, English

  [Refereed]

  In book


• Memory Trace in Feeding Neural Circuitry Underlying Conditioned Taste Aversion in Lymnaea

  Etsuro Ito, Emi Otsuka, Noriyuki Hama, Hitoshi Aonuma, Ryuichi Okada, Dai Hatakeyama, Yutaka Fujito, Suguru Kobayashi

  Background: The pond snail Lymnaea stagnalis can maintain a conditioned taste aversion (CTA) as a long-term memory. Previous studies have shown that the inhibitory postsynaptic potential (IPSP) evoked in the neuron 1 medial (N1M) cell by activation of the cerebral giant cell (CGC) in taste aversion-trained snails was larger and lasted longer than that in control snails. The N1M cell is one of the interneurons in the feeding central pattern generator (CPG), and the CGC is a key regulatory neuron for the feeding CPG. Methodology/Principle Findings: Previous studies have suggested that the neural circuit between the CGC and the N1M cell consists of two synaptic connections: (1) the excitatory connection from the CGC to the neuron 3 tonic (N3t) cell and (2) the inhibitory connection from the N3t cell to the N1M cell. However, because the N3t cell is too small to access consistently by electrophysiological methods, in the present study the synaptic inputs from the CGC to the N3t cell and those from the N3t cell to the N1M cell were monitored as the monosynaptic excitatory postsynaptic potential (EPSP) recorded in the large B1 and B3 motor neurons, respectively. The evoked monosynaptic EPSPs of the B1 motor neurons in the brains isolated from the taste aversion-trained snails were identical to those in the control snails, whereas the spontaneous monosynaptic EPSPs of the B3 motor neurons were significantly enlarged. Conclusion/Significance: These results suggest that, after taste aversion training, the monosynaptic inputs from the N3t cell to the following neurons including the N1M cell are specifically facilitated. That is, one of the memory traces for taste aversion remains as an increase in neurotransmitter released from the N3t cell. We thus conclude that the N3t cell suppresses the N1M cell in the feeding CPG, in response to the conditioned stimulus in Lymnaea CTA.

  PUBLIC LIBRARY SCIENCE, Aug. 2012, PLOS ONE, 7(8) (8), e43151, English

  [Refereed]

  Scientific journal


• Waggle dance effect: dancing in autumn reduces the mass loss of a honeybee colony

  Ryuichi Okada, Tadaaki Akamatsu, Kanako Iwata, Hidetoshi Ikeno, Toshifumi Kimura, Mizue Ohashi, Hitoshi Aonuma, Etsuro Ito

  A honeybee informs her nestmates about the location of a profitable food source that she has visited by means of a waggle dance: a round dance and a figure-of-eight dance for a short- and long-distance food source, respectively. Consequently, the colony achieves an effective collection of food. However, it is still not fully understood how much effect the dance behavior has on the food collection, because most of the relevant experiments have been performed only in limited locations under limited experimental conditions. Here, we examined the efficacy of the waggle dances by physically preventing bees from dancing and then analyzing the changes in daily mass of the hive as an index of daily food collection. To eliminate place-and year-specific effects, the experiments were performed under fully natural conditions in three different cities in Japan from mid September to early October in three different years. Because the experiments were performed in autumn, all six of the tested colonies lost mass on most of the experimental days. When the dance was prevented, the daily reduction in mass change was greater than when the dance was allowed, i.e. the dance inhibited the reduction of the hive mass. This indicates that dance is effective for food collection. Furthermore, clear inhibition was observed on the first two days of the experiments; after that, inhibition was no longer evident. This result suggests that the bee colony adapted to the new environment.

  COMPANY OF BIOLOGISTS LTD, May 2012, JOURNAL OF EXPERIMENTAL BIOLOGY, 215(10) (10), 1633 - 1641, English

  [Refereed]

  Scientific journal


• Evidence for instantaneous e-vector detection in the honeybee using an associative learning paradigm

  Midori Sakura, Ryuichi Okada, Hitoshi Aonuma

  Many insects use the polarization pattern of the sky for obtaining compass information during orientation or navigation. E-vector information is collected by a specialized area in the dorsal-most part of the compound eye, the dorsal rim area (DRA). We tested honeybees' capability of learning certain e-vector orientations by using a classical conditioning paradigm with the proboscis extension reflex. When one e-vector orientation (CS+) was associated with sugar water, while another orientation (CS-) was not rewarded, the honeybees could discriminate CS+ from CS-. Bees whose DRA was inactivated by painting did not learn CS+. When ultraviolet (UV) polarized light (350 nm) was used for CS, the bees discriminated CS+ from CS-, but no discrimination was observed in blue (442 nm) or green light (546 nm). Our data indicate that honeybees can learn and discriminate between different e-vector orientations, sensed by the UV receptors of the DRA, suggesting that bees can determine their flight direction from polarized UV skylight during foraging. Fixing the bees' heads during the experiments did not prevent learning, indicating that they use an 'instantaneous' algorithm of e-vector detection; that is, the bees do not need to actively scan the sky with their DRAs ('sequential' method) to determine e-vector orientation.

  Lead, ROYAL SOC, Feb. 2012, PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES, 279(1728) (1728), 535 - 542, English

  [Refereed]

  Scientific journal


• 1D1534 Insulin and glucose for memory in a snail(Development, Differentiation, Neuroscience,Oral Presentation,The 50th Annual Meeting of the Biophysical Society of Japan)

  Ito Etsuro, Okada Ryuichi, Morikawa Mika, Takigami Satoshi, Okuta Akiko, Sakakibara Manabu

  The Biophysical Society of Japan General Incorporated Association, 2012, Seibutsu Butsuri, 52, S26, English


• Tracking of Multiple Honey Bees on a Flat Surface

  Toshifumi Kimura, Mizue Ohashi, Karl Crailsheim, Thomas Schmickl, Ryuichi Okada, Hidetoshi Ikeno

  Social insects interact extensively with their mates. To reveal the mechanism of their sociality, it is important to observe the behavior of each individual in a colony and to analyze their social contexts. Recently, digital video cameras have become less expensive despite increases in their performance, enabling researchers to record the behavior in various places easily. However, much labor and time is needed to analyze the social behavior manually from the video footage. In this study, we propose a new method to detect and track multiple bees moving on a flat surface. Our proposed method consists of three core processes: (i) detecting the bee candidate regions using a background subtraction method and binarization, (ii) identifying individuals by a combination of overlapping information in temporal changes of position and simple prediction of the candidate regions based on the bee's movement, and (iii) outputting the locations and trajectories of the identified bees. Our system succeeds in processing a video of sixteen bees moving freely on a flat arena for three minutes. More than 95% of the bees' central points were successfully extracted and their trajectories precisely traced.

  IEEE, 2012, PROCEEDINGS OF THE 2012 FIFTH INTERNATIONAL CONFERENCE ON EMERGING TRENDS IN ENGINEERING AND TECHNOLOGY (ICETET 2012), 36 - 39, English

  [Refereed]

  International conference proceedings


• MATHEMATICAL ANALYSIS OF THE HONEYBEE WAGGLE DANCE

  R. Okada, H. Ikeno, T. Kimura, Mizue Ohashi, H. Aonuma, E. Ito

  A honeybee informs her nestmates of the location of a flower by doing a waggle dance. The waggle dance encodes both the direction of and distance to the flower from the hive. To reveal how the waggle dance benefits the colony, we created a Markov model of bee foraging behavior and performed simulation experiments by incorporating the biological parameters that we obtained from our own observations of real bees as well as from the literature. When two feeders were each placed 400 m away from the hive in different directions, a virtual colony in which honeybees danced and correctly transferred information (a normal, real bee colony) made significantly greater numbers of successful visits to the feeders compared to a colony with inaccurate information transfer. Howerer, when five feeders were each located 400 m from the hive, the inaccurate information transfer colony performed better than the normal colony. These results suggest that dancing's ability to communicate accurate information depends on the number of feeders. Furthermore, because non-dancing colonies always made significantly fewer visits than those two colonies, we concluded that dancing behavior is beneficial for hives' ability to visit food sources.

  AKADEMIAI KIADO RT, 2012, ACTA BIOLOGICA HUNGARICA, 63, 75 - 79, English

  [Refereed]

  Scientific journal


• INSULIN AND MEMORY IN LYMNAEA

  E. Ito, R. Okada, Yuki Sakamoto, Emi Otshuka, K. Mita, Akiko Okuta, H. Sunada, M. Sakakibara

  The pond snail, Lymnaea stagnalis, is capable of learning conditioned taste aversion (CTA) and consolidating this CTA into long-term memory (LTM). The DNA microarray experiments showed that some of molluscan insulin-related peptides (MIPs) were up-regulated in snails exhibiting CTA-LTM. On the other hand, the electrophysiological experiments showed that application of secretions from the MIPs-containing cells evoked long-term potentiation (LTP) at the synapses between the cerebral giant cell (a key interneuron for CTA) and the B1 motoneuron (a buccal motoneuron). We thus hypothesized that MIPs and MIP receptors play an important role at the synapses, probably underlying the CTA-LTM consolidation process. To examine this hypothesis, we applied the antibody, which recognizes the binding site of mammalian insulin receptors and is thought to cross-react MIP receptors, to the Lymnaea CNS. Our present data showed that an application of the antibody for insulin receptors to the isolated CNS blocked LTP, and that an injection of the antibody into the Lymnaea abdominal cavity inhibited LTM consolidation, but not CTA formation.

  AKADEMIAI KIADO RT, 2012, ACTA BIOLOGICA HUNGARICA, 63, 194 - 201, English

  [Refereed]

  Scientific journal


• A new approach for the simultaneous tracking of multiple honeybees for analysis of hive behavior

  Toshifumi Kimura, Mizue Ohashi, Ryuichi Okada, Hidetoshi Ikeno

  Social activities are among the most striking of animal behaviors, and the clarification of their mechanisms is a major subject in ethology. Honeybees are a good model for revealing these mechanisms because they display various social behaviors, such as division of labor, in their colonies. Image processing is a precise and convenient tool for obtaining animal behavior data, but even recent methods are inadequate for the identification or description of honeybee behavior. This is because of the difficulty distinguishing between the large number of individuals in a small hive and their multiple movements. The present study developed a new computer-aided system, using a vector quantization method, for the identification and behavioral tracking of individual honeybees. The vector quantization method enabled separation of honeybee bodies in photographs recorded as a movie. This system succeeded in analyzing a huge number of frames quickly and can thus save both time and labor. Moreover, the system identified more than 72% of the bees in a hive and found and determined the active areas in the hive by extracting the trajectories of walking bees. In addition, useful behavioral data on the honeybee waggle dance were obtained using the present system.

  SPRINGER FRANCE, Sep. 2011, APIDOLOGIE, 42(5) (5), 607 - 617, English

  [Refereed]

  Scientific journal


• Highly Sensitive Determination of Hydrogen Peroxide and Glucose by Fluorescence Correlation Spectroscopy

  Satoshi Watabe, Yuki Sakamoto, Mika Morikawa, Ryuichi Okada, Toshiaki Miura, Etsuro Ito

  Background: Because H2O2 is generated by various oxidase-catalyzed reactions, a highly sensitive determination method of H2O2 is applicable to measurements of low levels of various oxidases and their substrates such as glucose, lactate, glutamate, urate, xanthine, choline, cholesterol and NADPH. We propose herein a new, highly sensitive method for the measurement of H2O2 and glucose using fluorescence correlation spectroscopy (FCS).Methodology/Principal Findings: FCS has the advantage of allowing us to determine the number of fluorescent molecules. FCS measures the fluctuations in fluorescence intensity caused by fluorescent probe movement in a small light cavity with a defined volume generated by confocal illumination. We thus developed a highly sensitive determination system of H2O2 by FCS, where horseradish peroxidase (HRP) catalyzes the formation of a covalent bond between fluorescent molecules and proteins in the presence of H2O2. Our developed system gave a linear calibration curve for H2O2 in the range of 28 to 300 nM with the detection limit of 8 nM. In addition, by coupling with glucose oxidase (GOD)-catalyzed reaction, the method allows to measure glucose in the range of 80 nM to 1.5 mu M with detection limit of 24 nM. The method was applicable to the assay of glucose in blood plasma. The mean concentration of glucose in normal human blood plasma was determined to be 4.9 mM.Conclusions/Significance: In comparison with commercial available methods, the detection limit and the minimum value of determination for glucose are at least 2 orders of magnitude more sensitive in our system. Such a highly sensitive method leads the fact that only a very small amount of plasma (20 nL) is needed for the determination of glucose concentration in blood plasma.

  PUBLIC LIBRARY SCIENCE, Aug. 2011, PLOS ONE, 6(8) (8), e22955, English

  [Refereed]

  Scientific journal


• Markov Model of Honeybee Social Behavior

  Ryuichi Okada, Hidetoshi Ikeno, Toshifumi Kimura, Mizue Ohashi, Hitoshi Aonuma, Etsuro Ito

  It is well established that honeybees inform their nestmates of the location of flowers they have visited by a unique behavior called a "waggle dance". To evaluate the efficacy of this dance in terms of food collection, we constructed a Markov model for foraging behavior. The computer simulation showed that our model faithfully expressed actual bee behavior; revealed that a colony in which honeybees danced and correctly transferred information made 2.15 times more successful visits to food sources compared to a colony with non-accurate information transfer; and suggested that the waggle dance is effective only under particular conditions.

  INT INFORMATION INST, May 2010, INFORMATION-AN INTERNATIONAL INTERDISCIPLINARY JOURNAL, 13(3B) (3B), 1115 - 1130, English

  [Refereed]

  Scientific journal


• 3P257 Lon-term potentiation induced by insulin-like peptide in the central nervous system of a snail(Neuronal Circuit & Information processing,The 48th Annual Meeting of the Biophysical Society of Japan)

  Ito Etsuro, Murakami Jun, Okada Ryuichi, Okuta Akiko, Sadamoto Hisayo

  The Biophysical Society of Japan General Incorporated Association, 2010, Seibutsu Butsuri, 50(2) (2), S190, English


• Observation system for the control of the hive environment by the honeybee (Apis mellifera)

  Mizue Ohashi, Ryuichi Okada, Toshifumi Kimura, Hidetoshi Ikeno

  The honeybee can control its hive environment to survive drastic changes in the field environment. To study the control of multiple environmental factors by honeybees, in this experiment, we developed a continual and simultaneous monitoring system for the temperature, moisture, and carbon dioxide (CO(2)) concentration in a honeybee hive. Changes in hive weight, CO(2) production rate, and honeybee behavior were also monitored to estimate energy costs and behavioral activity for the environmental regulation. Measurements were conducted in August 2008. We found that the honeybee hive has a microclimate different from the ambient climate, and that the difference was partly accompanied by changes in honeybee activity. Our results also suggest that hive temperature, humidity, and CO(2) concentrations are controlled by different mechanisms. Additional monitoring of the hive environment and honeybee behavior for longer periods would enable us to understand the mechanisms of environmental control by honeybees, which is one of the behaviors that define honeybees as social insects.

  PSYCHONOMIC SOC INC, Aug. 2009, BEHAVIOR RESEARCH METHODS, 41(3) (3), 782 - 786, English

  [Refereed]

  Scientific journal


• Gamma-Aminobuyric Acid (GABA)-Mediated Neural Connections in the Drosophila Antennal Lobe

  Ryuichi Okada, Takeshi Awasaki, Kei Ito

  Inhibitory synaptic connections mediated by gamma-aminobutyric acid (GABA) play important roles in the neural computation of the brain. To obtain a detailed overview of the neural connections mediated by GABA signals, we analyzed the distribution of the cells that produce and receive GABA in the Drosophila adult brain. Relatively small numbers of the cells, which form clusters in several areas of the brain, express the GABA synthesis enzyme Gad1. On the other hand, many cells scattered across the brain express ionotropic GABA(A) receptor subunits (Lcch3 and Rdl) and metabotropic GABA(B) receptor subtypes (GABA-B-R1, -2, and -3). To analyze the expression of these genes in distinct identified cell types, we focused on the antennal lobe, where GABAergic neurons play important roles in odor coding. By combining fluorescent in situ hybridization and immunolabeling against GFP expressed with cell-type-specific GAL4 driver strains, we quantified the percentage of the cells that produce or receive GABA for each cell type. GABA was synthesized in the middle antennocerebral tract (mACT) projection neurons and two types of local neurons. Among them, mACT neurons had few presynaptic sites in the antennal lobe, making the local neurons essentially the sole provider of GABA signals there. On the other hand, not only these local neurons but also all types of projection neurons expressed both ionotropic and metabotropic GABA receptors. Thus, even though inhibitory signals are released from only a few, specific types of local neurons, the signals are read by most of the neurons in the antennal lobe neural circuitry. J. Comp. Neurol. 514:74-91, 2009. (c) 2009 Wiley-Liss, Inc.

  WILEY-LISS, May 2009, JOURNAL OF COMPARATIVE NEUROLOGY, 514(1) (1), 74 - 91, English

  [Refereed]

  Scientific journal


• The tracking system of honeybee behavior in the observation hive

  Toshifumi Kimura, Hidetoshi Ikeno, Mizue Ohashi, Ryuichi Okada, Etsuro Ito

  ELSEVIER SCIENCE INC, Dec. 2008, COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY B-BIOCHEMISTRY & MOLECULAR BIOLOGY, 151(4) (4), 455 - 456, English

  [Refereed]


• A movement index for evaluation of honeybee activity in the observation hive

  Hidetoshi Ikeno, Ryuichi Okada, Mizue Ohashi, Toshifumi Kimura, Tadaaki Akamatsu, Etsuro Ito

  ELSEVIER SCIENCE INC, Dec. 2008, COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY B-BIOCHEMISTRY & MOLECULAR BIOLOGY, 151(4) (4), 456 - 456, English

  [Refereed]


• Locomotion patterns of honeybee in the hive

  Ryuichi Okada, Hidetoshi Ikeno, Toshifumi Kimura, Mizue Ohashi, Hitoshi Aonuma, Etsuro Ito

  ELSEVIER SCIENCE INC, Dec. 2008, COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY B-BIOCHEMISTRY & MOLECULAR BIOLOGY, 151(4) (4), 456 - 456, English


• Olfactory Information Processing in the Drosophila Antennal Lobe: Anything Goes?

  Ana F. Silbering, Ryuichi Okada, Kei Ito, C. Giovanni Galizia

  When an animal smells an odor, olfactory sensory neurons generate an activity pattern across olfactory glomeruli of the first sensory neuropil, the insect antennal lobe or the vertebrate olfactory bulb. Here, several networks of local neurons interact with sensory neurons and with output neurons-insect projection neurons, or vertebrate mitral/tufted cells. The extent and form of information processing taking place in these local networks has been subject of controversy. To investigate the role of local neurons in odor information processing we have used the calcium sensor G-CaMP to perform in vivo recordings of odor-evoked spatiotemporal activity patterns in five genetically defined neuron populations of the antennal lobe of Drosophila melanogaster: three distinct populations of local neurons ( two GABAergic and one cholinergic), as well as sensory neurons and projection neurons. Odor-specific and concentration dependent spatiotemporal response patterns varied among neuron populations. Activity transfer differed along the olfactory pathway for different glomerulus-odor combinations: we found cases of profile broadening and of linear and complex transfer. Moreover, the discriminability between the odors also varied across neuron populations and was maximal in projection neurons. Discriminatory power increased with higher odor concentrations over a wide dynamic range, but decreased at the highest concentration. These results show the complexity and diversity of odor information processing mechanisms across olfactory glomeruli in the fly antennal lobe.

  SOC NEUROSCIENCE, Dec. 2008, JOURNAL OF NEUROSCIENCE, 28(49) (49), 13075 - 13087, English

  [Refereed]

  Scientific journal


• Drosophila olfactory local interneurons and projection neurons derive from a common neuroblast lineage specified by the empty spiracles gene

  Abhijit Das, Sonia Sen, Robert Lichtneckert, Ryuichi Okada, Kei Ito, Veronica Rodrigues, Heinrich Reichert

  Background: Encoding of olfactory information in insects occurs in the antennal lobe where the olfactory receptor neurons interact with projection neurons and local interneurons in a complex sensory processing circuitry. While several studies have addressed the developmental mechanisms involved in specification and connectivity of olfactory receptor neurons and projection neurons in Drosophila, the local interneurons are far less well understood. Results: In this study, we use genetic marking techniques combined with antibody labelling and neuroblast ablation to analyse lineage specific aspects of local interneuron development. We find that a large set of local interneurons labelled by the GAL4-LNI (NP1227) and GAL4-LN2 (NP2426) lines arise from the lateral neuroblast, which has also been shown to generate uniglomerular projection neurons. Moreover, we find that a remarkable diversity of local interneuron cell types with different glomerular innervation patterns and neurotransmitter expression derives from this lineage. We analyse the birth order of these two distinct neuronal types by generating MARCM (mosaic analysis with a repressible cell marker) clones at different times during larval life. This analysis shows that local interneurons arise throughout the proliferative cycle of the lateral neuroblast beginning in the embryo, while uniglomerular projection neurons arise later during the second larval instar. The lateral neuroblast requires the function of the cephalic gap gene empty spiracles for the development of olfactory interneurons. In empty spiracles null mutant clones, most of the local interneurons and lateral projection neurons are lacking. These findings reveal similarities in the development of local interneurons and projection neurons in the olfactory system of Drosophila. Conclusion: We find that the lateral neuroblast of the deutocerebrum gives rise to a large and remarkably diverse set of local interneurons as well as to projection neurons in the antennal lobe. Moreover, we show that specific combinations of these two neuron types are produced in specific time windows in this neuroblast lineage. The development of both these cell types in this lineage requires the function of the empty spiracles gene.

  BIOMED CENTRAL LTD, Dec. 2008, NEURAL DEVELOPMENT, 3, 33, English

  [Refereed]

  Scientific journal


• The dance of the honeybee: How do honeybees dance to transfer food information effectively?

  R. Okada, H. Ikeno, Noriko Sasayama, H. Aonuma, D. Kurabayashi, E. Ito

  A honeybee informs her nestmates of the location of a flower she has visited by a unique behavior called a "waggle dance." On a vertical comb, the direction of the waggle run relative to gravity indicates the direction to the food source relative to the sun in the field, and the duration of the waggle run indicates the distance to the food source. To determine the detailed biological features of the waggle dance, we observed worker honeybee behavior in the field. Video analysis showed that the bee does not dance in a single or random place in the hive but waggled several times in one place and then several times in another. It also showed that the information of the waggle dance contains a substantial margin of error. Angle and duration of waggle runs varied from run to run, with the range of +/- 15 degrees and +/- 15%, respectively, even in a series of waggle dances of a single individual. We also found that most dance followers that listen to the waggle (lance left the dancer after one or two sessions of listening.

  AKADEMIAI KIADO, 2008, ACTA BIOLOGICA HUNGARICA, 59, 157 - 162, English

  [Refereed]

  Scientific journal


• Speed of back-swimming of Lymnaea

  Kanako Aono, A. Fusada, Y. Fusada, W. Ishii, Y. Kanaya, Mami Komuro, Kanae Matsui, S. Meguro, Ayumi Miyamae, Yurie Miyamae, Aya Murata, Shizuka Narita, Hiroe Nozaka, Wakana Saito, Ayumi Watanabe, Kaori Nishikata, A. Kanazawa, Y. Fujito, R. Okada, K. Lukowiak, E. Ito

  The pond snail, Lymnaea stagnalis, can locomote on its back utilizing the surface tension of the water. We have called this form of movement 'back-swimming'. In order to perform this behavior, the snail must flip itself over on its back so that its foot is visible from above. Little is known about the mechanism of this back-swimming. As a first step for the elucidation of this mechanism, we measured the speed of back-swimming of Lymnaea at the different times of the day. They back-swam significantly faster in the morning than just before dark. These data are consistent with Our earlier findings on circadian-timed activity pattern in Lymnaea.. Lymnaea appear to secrete a thin membrane-like substance from their foot that may allow them to back-swim. To confirm the existence of this substance and to examine whether this substance is hydrophobic or hydrophilic, we applied a detergent onto the foot during back-swimming. A single drop of 1% Tween 20 drifted Lymnaea away that were still kept at the water surface. These results suggest that Lymnaea secrete a hydrophobic substance from their foot that floats to the water surface allowing Lymnaea to back-swim.

  AKADEMIAI KIADO, 2008, ACTA BIOLOGICA HUNGARICA, 59, 105 - 109, English

  [Refereed]

  Scientific journal


• Biological insights into robotics: honeybee foraging behavior by waggle dance

  OKADA Ryuichi, IKENO Hidetoshi, AONUMA Hitoshi, ITO Etsuro

  2008, Advanced Robotics, 22, 1665 - 1681, English

  [Refereed]

  Scientific journal


• Activity-dependent plasticity in an olfactory circuit

  Silke Sachse, Erroll Rueckert, Andreas Keller, Ryuichi Okada, Nobuaki K. Tanaka, Kei Ito, Leslie B. Vosshall

  Olfactory sensory neurons (OSNs) form synapses with local interneurons and second-order projection neurons to form stereotyped olfactory glomeruli. This primary olfactory circuit is hard-wired through the action of genetic cues. We asked whether individual glomeruli have the capacity for stimulus-evoked plasticity by focusing on the carbon dioxide (CO(2)) circuit in Drosophila. Specialized OSNs detect this gas and relay the information to a dedicated circuit in the brain. Prolonged exposure to CO(2) induced a reversible volume increase in the CO(2)-specific glomerulus. OSNs showed neither altered morphology nor function after chronic exposure, but one class of inhibitory local interneurons showed significantly increased responses to CO(2). Two-photon imaging of the axon terminals of a single PN innervating the CO(2) glomerulus showed significantly decreased functional output following CO(2) exposure. Behavioral responses to CO(2) were also reduced after such exposure. We suggest that activity-dependent functional plasticity may be a general feature of the Drosophila olfactory system.

  CELL PRESS, Dec. 2007, NEURON, 56(5) (5), 838 - 850, English

  [Refereed]

  Scientific journal


• Learning-related plasticity in PE1 and other mushroom body-extrinsic neurons in the honeybee brain

  Ryuichi Okada, Jurgen Rybak, Gisela Manz, Randolf Menzel

  Extracellular recording were performed from mushroom body-extrinsic neurons while the animal was exposed to differential conditioning to two odors, the forward-paired conditioned stimulus (CS+; the odor that will be or has been paired with sucrose reward) and the unpaired CS-(the odor that will be or has been specifically unpaired with sucrose reward). A single neuron, the pedunculus-extrinsic neuron number 1 ( PE1), was identified on the basis of its firing pattern, and other neurons were grouped together as non-PE1 neurons. PE1 reduces its response to CS+ and does not change its response to CS- after learning. Most non-PE1 neurons do not change their responses during learning, butsomedecrease, and one neuron increases its response to CS+. PE1 receives inhibitory synaptic inputs, and neuroanatomical studies indicate closely attached GABA-immune reactive profiles originating at least partially from neurons of the protocerebral -calycal tract (PCT). Thus, either the associative reduction of odor responses originates within the PE1 via a long-term depression (LTD)-like mechanism, or PE1 receives stronger inhibition for the learned odor from the PCT neurons or from Kenyon cells. In any event, as the decreased firing of PE1 correlates with the increased probability of behavioral responses, our data suggest that the mushroom bodies exert general inhibition over sensory -motor connections, which relaxes selectively for learned stimuli.

  SOC NEUROSCIENCE, Oct. 2007, JOURNAL OF NEUROSCIENCE, 27(43) (43), 11736 - 11747, English

  [Refereed]

  Scientific journal


• Cautionary observations on preparing and interpreting brain images using molecular biology-based staining techniques

  K Ito, R Okada, NK Tanaka, T Awasaki

  Though molecular biology-based visualization techniques such as antibody staining, in situ hybridization, and induction of reporter gene expression have become routine procedures for analyzing the structures of the brain, precautions to prevent misinterpretation have not always been taken when preparing and interpreting images. For example, sigmoidal development of the chemical processes in staining might exaggerate the specificity of a label. Or, adjustment of exposure for bright fluorescent signals might result in overlooking weak signals. Furthermore, documentation of a staining pattern is affected easily by recognized organized features in the image while other parts interpreted as "disorganized" may be ignored or discounted. Also, a higher intensity of a label per cell can often be confused with a higher percentage of labeled cells among a population. The quality, and hence interpretability, of the three-dimensional reconstruction with confocal microscopy can be affected by the attenuation of fluorescence during the scan, the refraction between the immersion and mounting media, and the choice of the reconstruction algorithm. Additionally, visualization of neurons with the induced expression of reporter genes can suffer because of the low specificity and low ubiquity of the expression drivers. The morphology and even the number of labeled cells can differ considerably depending on the reporters and antibodies used for detection. These aspects might affect the reliability of the experiments that involves induced expression of effector genes to perturb cellular functions. Examples of these potential pitfalls are discussed here using staining of Drosophila brain. (C) 2003 Wiley-Liss, Inc.

  WILEY-LISS, Oct. 2003, MICROSCOPY RESEARCH AND TECHNIQUE, 62(2) (2), 170 - 186, English

  [Refereed]

  Scientific journal


• Distribution of dendrites of descending neurons and its implications for the basic organization of the cockroach brain

  R Okada, M Sakura, M Mizunami

  To determine precisely the brain areas from which descending neurons (DNs) originate, we examined the distribution of somata and dendrites of DNs in the cockroach brain by retrogradely filling their axons from the cervical connective. At least 235 pairs of somata of DNs were stained, and most of these were grouped into 22 clusters. Their dendrites were distributed in most brain areas, including lateral and medial protocerebra, which are major termination areas of output neurons of the mushroom body, but not in the optic and antennal lobes, the mushroom body, the central complex, or the posteroventral part of the lateral horn. The last area is the termination area of major types of olfactory projection neurons from the antennal lobe, i.e., uni- and macroglomerular projection neurons, so these neurons have no direct connections with DNs. The distribution of axon terminals of ascending neurons overlaps with that of DN dendrites. We propose, based on these findings, that there are numerous parallel processing streams from cephalic sensory areas to thoracic locomotory centers, many of which are via premotor brain areas from which DNs originate. In addition, outputs from the mushroom body, central complex, and posteroventral part of the lateral horn converge on some of the premotor areas, presumably to modulate the activity of some sensorimotor pathways. We propose, based on our results and documented findings, that many parallel processing streams function in various forms of reflexive and relatively stereotyped behaviors, whereas indirect pathways govern some forms of experience-dependent modification of behavior.

  Lead, WILEY-LISS, Mar. 2003, JOURNAL OF COMPARATIVE NEUROLOGY, 458(2) (2), 158 - 174, English

  [Refereed]

  Scientific journal


• Olfactory discrimination of structurally similar alcohols by cockroaches

  M Sakura, R Okada, M Mizunami

  The capability of the cockroach Periplaneta americana to discriminate odors of structurally similar aliphatic alcohols was studied by using an operant conditioning paradigm. Cockroaches were trained to discriminate three odors: one odor associated with sucrose solution (reward) and two odors associated with NaCl solution (non-reward). After training, their odor preferences were tested by counting the number of visits to each odor source. We tested the capability of cockroaches to discriminate (1) three normal aliphatic alcohols with different numbers of carbon (1-pentanol, 1-hexanol and 1-octanol), (2) three C6 aliphatic alcohols (1-hexanol, 2-hexanol and trans-2-hexen-1-ol), (3) binary mixtures of two of these three alcohols and their components, and (4) 1-hexanol solution of three different concentrations (1, 10 and 100 mug mul(-1)). Cockroaches exhibited higher preferences for the odors associated with reward in these tests, and we therefore conclude that cockroaches can discriminate these odors. However, discrimination of 1-hexanol and trans-2-hexen-1-ol and their binary mixture was imperfect, in that some statistical tests suggested significant level of discrimination but other tests did not. In addition, the cockroaches learned to associate a 1-hexanol solution of the highest or lowest concentration with sucrose reward but failed to learn to associate 1-hexanol of an intermediate concentration with reward.

  SPRINGER-VERLAG, Nov. 2002, JOURNAL OF COMPARATIVE PHYSIOLOGY A-NEUROETHOLOGY SENSORY NEURAL AND BEHAVIORAL PHYSIOLOGY, 188(10) (10), 787 - 797, English

  [Refereed]

  Scientific journal


• Sensory responses and movement-related activities in extrinsic neurons of the cockroach mushroom bodies

  R Okada, J Ikeda, M Mizunami

  We have previously reported that most units in the input regions of the cockroach mushroom bodies have activities related to sensory inputs, while the majority of units in the output regions are related to movements of the animal. In the present study, we were able to attain a more satisfactory isolation of single units by using thinner wires and further characterize the activities of units in the mushroom body output regions. Forty-one units recorded here were classified into three types: sensory, movement-related, and sensori-motor units. Different units from each group exhibited a great variety in activities. Some movement-related and sensori-motor units exhibited activity preceding the onset of movements. We propose that the mushroom body participates in the integration of a variety of sensory and motor signals, possibly for initiating and maintaining motor action. While different neurons displayed a great diversity of responses, the activities of multiple neurons recorded simultaneously exhibited similar, but not identical, responses. These neurons appeared to locate adjacent to each other and may represent a cluster of extrinsic neurons that act synergistically to transmit a specific set of mushroom body output signals.

  Lead, SPRINGER VERLAG, Aug. 1999, JOURNAL OF COMPARATIVE PHYSIOLOGY A-SENSORY NEURAL AND BEHAVIORAL PHYSIOLOGY, 185(2) (2), 115 - 129, English

  [Refereed]

  Scientific journal


• Mushroom bodies of the cockroach: Activity and identities of neurons recorded in freely moving animals

  M Mizunami, R Okada, YS Li, NJ Strausfeld

  This article describes novel attributes of the mushroom bodies of cockroaches revealed by recording from neurons in freely moving insects. The results suggest several hitherto unrecognized functions of the mushroom bodies: extrinsic neurons that discriminate between imposed and self-generated sensory stimulation, extrinsic neurons that monitor motor actions, and a third class of extrinsic neurons that predict episodes of locomotion and modulate their activity depending on the turning direction. Electrophysiological units have been correlated with neurons that were partially stained by uptake of copper ions and silver intensification. Neurons so revealed correspond to Golgi-impregnated or Lucifer yellow-filled neurons and demonstrate that their processes generally ascend to other areas of the protocerebrum The present results support the idea of multiple roles for the mushroom bodies. These include sensory discrimination, the integration of sensory perception with motor actions, and, as described in the companion article, a role in place memory. J. Comp. Neurol. 402:501-519, 1998. (C) 1998 Wiley-Liss, Inc.

  WILEY-BLACKWELL, Dec. 1998, JOURNAL OF COMPARATIVE NEUROLOGY, 402(4) (4), 501 - 519, English

  [Refereed]

  Scientific journal


• Topography of modular subunits in the mushroom bodies of the cockroach

  M Mizunami, M Iwasaki, R Okada, M Nishikawa

  The mushroom body (MB), a conspicuous neuropil structure in the insect brain, is implicated in associative memory and in some aspects of motor control. Intrinsic neurons of the MB (Kenyon cells) extend dendrites into the calyx, and their axons run through the pedunculus and then bifurcate to form the alpha and the beta lobes. At the pedunculus and the lobes, Kenyon cells make synaptic connections with dendrites of extrinsic (output) neurons. Previously, we reported that the oc lobe of the cockroach MB consists of repetitive modular subunits (Mizunami et al. [1997] Neurosci. Lett. 229:153-156). Each subunit is composed of a dark layer and a light layer, and the layers are refereed to as slabs. Each slab is composed of axons of a specific subset of Kenyon cells. In the present study, we examined serial sections of reduced silver preparations and found that each dark and light slab continues throughout the length of the pedunculus and the alpha and beta lobes. We also found that Golgi-impregnated Kenyon cells often exhibit a characteristic grouping, forming a thin sheet interlaced by dozens or hundreds of axons. The sheet is much thinner than the slab, and each sheet remains within a particular slab throughout the length of the pedunculus and the lobes. Thus, the sheet is a component forming the slab. In the pedunculus and the beta lobe, a class of Golgi-impregnated extrinsic neurons exhibit segmented dendritelike arbors that interact with every other slab, i.e., either with only dark or light slabs. Because each neuron of this class interacts with each particular set of dark or light slabs, we conclude that the slabs are units for transmitting output signals from the MB. J. Comp. Neurol. 399:153-161, 1998. (C) 1998 Wiley-Liss, Inc.

  WILEY-LISS, Sep. 1998, JOURNAL OF COMPARATIVE NEUROLOGY, 399(2) (2), 153 - 161, English

  [Refereed]

  Scientific journal


• Topography of four classes of Kenyon cells in the mushroom bodies of the cockroach

  M Mizunami, M Iwasaki, R Okada, M Nishikawa

  Mushroom bodies (MBs), which are higher centers in the insect brain, are implicated in associative memory and in the control of some behaviors. Intrinsic neurons of the MB, called Kenyon cells, receive synaptic inputs from axon terminals of input neurons in the calyx. Axons of Kenyon cells project into the pedunculus and to the alpha and beta lobes, where they make synaptic connections with dendrites of extrinsic (output) neurons. In this study, we examined the morphology of Kenyon cells in the cockroach by using Golgi stains and found that they can be classified into four classes (K1, K2, K3, and K4), according to the diameter, location, and morphology of the cell bodies, dendrites, and axons. The somata of Kenyon cells of different classes occupy different concentric zones; K1 cells occupy the most central zone, and K4 cells occupy the most peripheral zone. The main processes of Kenyon cells of different classes also occupy different concentric zones in the calyx. Dendrites of K2 and K3 cells are distributed throughout the calycal neuropil, whereas those of K1 and K4 cells cover the outer and inner halves of the depth of the neuropil, respectively. In the pedunculus and the alpha and beta lobes, axons of Kenyon cells of different classes occupy different zones, although the separation is not complete. A class of extrinsic neurons in the alpha lobe has dendrite-like arbors that cover the zones where either K1, K2, or K3 are located. These neurons probably transmit signals of each class of Kenyon cells. We conclude that, in the cockroach, four classes of Kenyon cells subdivide the cell body region, pedunculus, and lobes of the MBs, whereas subdivision is less prominent in the calycal neuropil. J. Comp. Neurol. 399:162-175, 1998. (C) 1998 Wiley-Liss, Inc.

  WILEY-LISS, Sep. 1998, JOURNAL OF COMPARATIVE NEUROLOGY, 399(2) (2), 162 - 175, English

  [Refereed]

  Scientific journal


• Modular structures in the mushroom body of the cockroach

  M Mizunami, M Iwasaki, M Nishikawa, R Okada

  The mushroom body (MB) is a higher center of the insect brain and is critical to olfactory and other forms of associative memory. Here, we report that repetitive modular subunits, which we refer to as slabs, are present in the internal matrix of the alpha lobe, a major output neuropil of the MB in the cockroach. The methods employed were osmium-ethyl gallate, Bodian-reduced silver, and Golgi staining procedures. A total of 15 dark and 15 pale slabs, each consisting of specific subsets of intrinsic neurons (Kenyon cells), alternate throughout the length of the alpha lobe. One of the major classes of MB output neurons, which are postsynaptic to Kenyon cells, exhibited segmented dendritic arbors that interact with every other slabs, i.e. only either dark or pale slabs. As each output neuron interacts with each specific set of dark or pale slabs, the slab likely functions as a unit for transmitting MB output signals. (C) 1997 Elsevier Science Ireland Ltd.

  ELSEVIER SCI IRELAND LTD, Jul. 1997, NEUROSCIENCE LETTERS, 229(3) (3), 153 - 156, English

  [Refereed]

  Scientific journal

• 飛翔時間がカシナガの姿勢に及ぼす影響~フライトミルを用いた観察~

  小西温輝, 大橋瑞江, 池野英利, 岡田龍一, 山崎理正, 伊東康人

  2024, 日本森林学会大会学術講演集, 135th


• カシノナガキクイムシの宿主選択に関わる揮発性物質に対する触角の応答

  岡田龍一, 伊東康人, 山崎理正

  2024, 日本応用動物昆虫学会大会講演要旨, 68th


• カシノナガキクイムシにおける嗅覚1次中枢の構造と集合フェロモンの情報処理機構

  岡田龍一, 山崎理正, 伊東康人

  2021, 日本応用動物昆虫学会大会講演要旨, 65th


• Causes of high variation in flight distance of the ambrosia beetle Platypus quercivorus

  山崎理正, PHAM Duy Long, 伊東康人, 岡田龍一, 池野英利

  2021, 日本生態学会大会講演要旨(Web), 68th


• カシノナガキクイムシの嗅覚1次中枢の構造と集合フェロモンに対する応答

  岡田龍一, 山崎理正, 伊東康人

  2020, 日本応用動物昆虫学会大会講演要旨, 64th


• フライトミルによるカシノナガキクイムシ飛翔行動の活性化要因の解明

  藤原聖真, 山崎理正, 岡田龍一, PHAM Duy Long, 伊東康人, 池野英利

  2020, 日本森林学会大会学術講演集, 131st


• Flight behaviors of the ambrosia beetle Platypus quercivorus revealed by a flight mill

  PHAM DUY Long, ITO Yasuo, OKADA Ryuichi, IKENO Hidetoshi, YAMASAKI Michimasa

  Mar. 2019, 日本森林学会大会学術講演集, 130th, 167, English

  Summary national conference


• 集合フェロモン濃度変化がカシノナガキクイムシ飛翔特性に及ぼす影響

  石野貴大, 岡田龍一, 伊東康人, PHAM Long Duy, 山崎理正, 池野英利

  26 Mar. 2018, 日本森林学会大会学術講演集, 129th, 177, Japanese


• Behavioral responses of the ambrosia beetle Platypus quercivorus to chemical volatiles from host leaves

  PHAM DUY Long, YAMASAKI Michimasa, ITO Yasuto, OKADA Ryuichi, IKENO Hidetoshi

  Mar. 2018, 日本森林学会大会学術講演集, 129th, 176, English

  Summary national conference


• ミツバチの天空コンパスナビゲーション-空を見て方向を知るしくみ

  SAKURA MIDORI, 岡田 龍一

  Jan. 2018, 生物の科学 遺伝, 72(1) (1), 2 - 6, Japanese

  [Refereed]

  Introduction commerce magazine


• ミツバチの天空コンパスナビゲーション ―空を見て方向を知るしくみ

  SAKURA Midori, Okada Ryuichi

  Jan. 2018, 生物の科学 遺伝, 72, 2 - 6, Japanese

  Introduction scientific journal


• 集合フェロモンによってカシノナガキクイムシの飛翔特性に違いが生じるか?

  奥田直人, 岡田龍一, PHAM Long Duy, 伊東康人, 山崎理正, 池野英利

  Mar. 2017, 日本森林学会大会学術講演集, 128th, 133, Japanese

  Summary national conference


• ミツバチコロニーのエネルギー収支の見積もり-成長期と退行期の比較

  吉田澪, 大橋瑞江, 木村敏文, 岡田龍一, 池野英利

  2017, 日本生態学会大会講演要旨(Web), 64th


• 昆虫の脳と匂いの記憶

  岡田 龍一

  2017, アグリバイオ, 1, 76 - 81, Japanese

  Introduction commerce magazine


• What is ability for flight of the Platypus quercivorus decided by

  Fukaya Satoshi, Okuda Naoto, Okada Ryuiti, Ito Yasuto, Ikeno Hidetoshi, Yamasaki Mitimasa

  [in Japanese]

  THE JAPANESE FORESTRY SOCIETY, Mar. 2016, The Japanese Forest Society Congress, 127th, 225 - 151, Japanese

  Summary national conference


• ミツバチの採餌行動におけるエネルギー収支

  澤井穂高, 岡田龍一, 吉田澪, 大橋瑞江, 木村敏文, 池野英利

  2016, 日本生態学会大会講演要旨(Web), 63th


• ミツバチコロニーにおける採餌活動の日的変化および季節的変化の解析

  吉田澪, 大橋瑞江, 木村敏文, 岡田龍一, 池野英利

  2015, 日本生態学会大会講演要旨(Web), 62nd


• 空間を考慮したミツバチの巣板モデルとシミュレーション

  中桐斉之, 大橋瑞江, 岡田龍一, 池野英利

  2015, 日本生態学会大会講演要旨(Web), 62nd


• 昆虫の脳と匂いの記憶

  岡田 龍一

  ニューサイエンス社, 2015, 昆虫と自然, 50(14) (14), 40 - 44, Japanese

  Introduction commerce magazine


• ミツバチコロニーの生存維時における8の字ダンスの効果

  岡田龍一, 栄美紗, 木村敏文, 大橋瑞江, 池野英利

  2014, 日本動物学会大会予稿集, 85th


• 「脳科学のフロンティア」 脳はどこまでわかってきたか：神経可塑性に着目して

  岡田 龍一, 伊藤 悦朗

  丸善, 2013, パリティ, 28(4) (4), 24 - 32, Japanese

  [Refereed]

  Introduction commerce magazine


• Involvement of nitric oxide in memory formation in microbrains

  ITO Etsuro, MATSUO Ryota, OKADA Ryuichi

  2013, Neuroscience Letters, 541, 1 - 3, English

  [Refereed]

  Introduction scientific journal


• 動的環境下でのミツバチ採餌行動におけるダンス情報の誤差の効果

  岡田龍一, 池野英利, 木村敏文, 大橋瑞江, 青沼仁志, 伊藤悦朗

  20 Aug. 2012, 日本動物学会大会予稿集, 83rd, 128, Japanese


• モノアラガイの長期記憶におけるインスリンとグルコースの役割

  伊藤悦朗, 箕田康一, 岡田龍一, 森川美佳, 山岸美貴, 大塚栄美

  2012, 日本動物学会中国四国支部会報, (64) (64), 20, Japanese


• ミツバチの尻振りダンスと採餌行動における効果

  岡田 龍一

  2012, 比較生理生化学, 29, 121 - 130, Japanese

  [Refereed]

  Introduction scientific journal


• コンピュータシミュレーションによるミツバチ8の字ダンスの採餌行動における効果

  岡田龍一, 池野英利, 木村敏文, 大橋瑞江, 青沼仁志, 伊藤悦朗

  20 Aug. 2011, 日本動物学会大会予稿集, 82nd, 145, Japanese


• コンピュータシミュレーションによるミツバチの採餌戦略の解析

  岡田龍一, 池野英利, 木村敏文, 大橋瑞江, 青沼仁志, 伊藤悦朗

  2011, 日本動物学会中国四国支部会報, (63) (63), 16, Japanese


• 計算機シミュレーションによるミツバチ8の字ダンスの採餌行動における効果

  岡田龍一, 池野英利, 木村敏文, 大橋瑞江, 青沼仁志, 伊藤悦朗

  20 Aug. 2010, 日本動物学会大会予稿集, 81st, 155, Japanese


• 数理モデルによるミツバチの8の字ダンスの生物的意義の解析

  岡田龍一, 池野英利, 木村敏文, 大橋瑞江, 青沼仁志, 伊藤悦朗

  2010, 日本比較生理生化学会大会予稿集, 32nd, 29, Japanese


• ミツバチの採餌行動は尻振りダンス行動によって効率的になるのか?

  岡田龍一, 池野英利, 赤松忠明, 岩田可南子, 木村敏文, 大橋瑞江, 青沼仁志, 伊藤悦朗

  2010, 日本動物学会中国四国支部会報, (62) (62), 12, Japanese


• Effects of a waggle dance on the honeybee foraging behavior

  岡田龍一, 池野英利, 木村敏文, 大橋瑞江, 青沼仁志, 伊藤悦朗

  2009, 日本動物学会大会予稿集, 80th (Web)


• Tracking system of plural honeybees for behavioral analysis

  木村敏文, 池野英利, 大橋瑞江, 岡田龍一

  2009, 日本動物学会大会予稿集, 80th (Web)


• Analysis of carbon flow using continuous measuring system in honeybee colony

  岩田可南子, 池野英利, 大橋瑞江, 木村敏文, 岡田龍一, 赤松忠明

  2009, 日本動物学会大会予稿集, 80th (Web)


• ミツバチの尻振りダンスとコロニーの集蜜量の関係

  岡田龍一, 赤松忠明, 岩田可南子, 池野英利, 木村敏文, 大橋瑞江, 青沼仁志, 伊藤悦朗

  2009, 日本比較生理生化学会大会予稿集, 31st, 69, Japanese


• セイヨウミツバチの偏光知覚機構の解明

  佐倉緑, 岡田龍一, 青沼仁志

  2009, 日本比較生理生化学会大会予稿集, 31st, 70, Japanese


• ショウジョウバエ脳のGABAニューロンの局在と役割

  岡田 龍一, 伊藤 啓

  2009, 生体の科学, 60, 394 - 395, Japanese

  Introduction scientific journal


• 巣内での追従バチの行動パターン

  岡田龍一, 池野英利, 木村敏文, 大橋瑞江, 青沼仁志, 伊藤悦朗

  20 Aug. 2008, 日本動物学会大会予稿集, 79th, 132, Japanese


• A basic study of tracking honeybees in the observation hive using vector quantization method

  KIMURA Toshifumi, IKENO Hidetoshi, OHASHI Mizue, OKADA Ryuichi, ITO Etsuro

  The analysis of biological function produced by both of individual and assemblage activity of animals is a challenging topic of behavioral ecology. Social insects are possible tool for the analysis because numerous studies have been already done to clarify the behavioral factors of individuals. Especially, honeybee is an ideal animal for the experiments because of the development of breeding techniques, existence of clear caste according to their age, efficient forage behavior adaptive for variable feeding places and high ability of honey storage in their colony. Seeley et al. conducted many behavioral experiments in order to scrutinize honeybee behavior inside and outside of the nests. However, these experiments normally have to put numbers on each body of thousands of honeybees to identify individuals and follow their behavior by hand, which require huge time and labors. In this study, we developed a system to identify honeybee in a nest image and to follow plural honeybees simultaneously. The system is composed by three parts, determination of the region of honeybee body from the other parts with vector quantization, extraction of the region of single honeybee bodies, and reorganization of single honeybees. Our system succeeded to identify nearly 70% of honeybees in a hive automatically.

  The Institute of Electronics, Information and Communication Engineers, 06 Mar. 2008, IEICE technical report, 107(541) (541), 113 - 116, Japanese


• 巣内ミツバチ活動を評価するための時空間運動指標

  池野英利, 岡田龍一, 大橋瑞江, 木村敏文, 赤松忠明, 伊藤悦朗

  2008, 日本比較生理生化学会大会予稿集, 30th


• ミツバチの観察巣板内行動追跡システム

  木村敏文, 池野英利, 大橋瑞江, 岡田龍一, 伊藤悦朗

  2008, 日本比較生理生化学会大会予稿集, 30th


• 巣内ミツバチの歩行パターン

  岡田龍一, 池野英利, 木村敏文, 大橋瑞江, 青沼仁志, 伊藤悦朗

  2008, 日本比較生理生化学会大会予稿集, 30th, 29, Japanese


• 社会的適応行動から学ぶ情報共有システムの構築―ミツバチの８の字ダンスを対象として

  岡田 龍一, 池野 英利, 青沼 仁志, 倉林 大輔, 伊藤 悦朗

  2007, 計測と制御, 46, 916 - 921, Japanese

  [Refereed]

  Introduction scientific journal


• The basic design of the insect brain for motor control

  Ryuichi Okada

  ELSEVIER SCIENCE INC, Nov. 2006, COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY B-BIOCHEMISTRY & MOLECULAR BIOLOGY, 145(3-4) (3-4), 401 - 401, English

  Summary international conference


• Distribution of dendrites of descending neurons and its implications for the basic organization of the cockroach brain. (vol 458, pg 158, 2003)

  R Okada, M Sakura, M Mizunami

  To determine precisely the brain areas from which descending neurons (DNs) originate, we examined the distribution of somata and dendrites of DNs in the Cockroach brain by retrogradely filling their axons from the cervical connective. At least 235 pairs of somata of DNs were stained, and most of these were grouped into 22 clusters. Their dendrites were distributed in most brain areas, including lateral and medial protocerebra, which are major termination areas of output neurons of the mushroom body, but not in the optic and antennal lobes, the mushroom body, the central complex, or the posteroventral part of the lateral horn. The last area is the termination area of major types of olfactory projection neurons from the antennal lobe, i.e., uni- and macroglomerular projection neurons, so these neurons have no direct connections with DNs. The distribution of axon terminals of ascending neurons overlaps with that of DN dendrites. We propose, based on these findings, that there are numerous parallel processing streams from cephalic sensory areas to thoracic locomotory centers, many of which are via premotor brain areas from which DNs originate. In addition, outputs from the mushroom body, central complex, and posteroventral part of the lateral horn converge on some of the premotor areas, presumably to modulate the activity of some sensorimotor pathways. We propose, based on our results and documented findings, that many parallel processing streams function in various forms of reflexive and relatively stereotyped behaviors, whereas indirect pathways govern some forms of experience-dependent modification of behavior. (C) 2003 Wiley-Liss, Inc.

  WILEY-LISS, May 2003, JOURNAL OF COMPARATIVE NEUROLOGY, 459(3) (3), 327 - +, English

  Others


• 昆虫の嗅覚学習

  水波 誠, 松本 幸久, 佐倉 緑, 岡田 龍一

  北海道大学, 1999, 電子科学研究, 7, 69 - 71, Japanese

• 研究者が教える動物実験 第３巻：行動

  OKADA RYUICHI, SAKURA MIDORI, AI HIROYUKI

  Joint work, 共立出版, 2015, Japanese

  General book


• 研究者が教える動物実験 第２巻：神経・筋

  OKADA RYUICHI

  Joint work, 共立出版, 2015, Japanese

  General book


• 研究者が教える動物実験 第１巻：感覚

  OKADA RYUICHI

  Joint work, 共立出版, 2015, Japanese

  General book


• Memory Consolidation

  OKADA RYUICHI

  Joint work, NOVA Science Publisher, 2015, English

  Scholarly book


• ミツバチのダンス ダンス 「行動生物学辞典」

  OKADA RYUICHI

  Joint work, 東京化学同人, 2013, Japanese

  Dictionary or encycropedia


• 分子昆虫学 −ポストゲノムの昆虫研究−

  OKADA RYUICHI

  Joint work, 共立出版, 2009, Japanese

  Scholarly book


• 身近な動物を使った実験４ ミツバチ コオロギ スズメガ

  OKADA RYUICHI

  Joint work, 三共出版, 2009, Japanese

  General book

• Life history of navigational exploration and social communication in honeybees

  Chen X, Okada R, Walter S, Sakura M, Xing Y, Menzel R

  13th Göttingen Meeting of the German Neuroscience Society, Mar. 2019, English, Göttingen, Germany, International conference

  Poster presentation


• Place memory based on visual information in the cricket Gryllus bimaculatus

  Matsubara N, Okada R, Sakura M

  日本比較生理学会第40回神戸大会, Nov. 2018, English, 神戸, Domestic conference

  Poster presentation


• ミツバチの嗅覚－味覚連合学習におけるオクトパミンの役割

  小林 樹里, 岡田 龍一, 佐倉 緑

  日本動物学会第89回札幌大会, Sep. 2018, Japanese, 札幌, Domestic conference

  Poster presentation


• フタホシコオロギの視覚情報に基づく場所記憶形成

  松原 伸明, 岡田 龍一, 佐倉 緑

  日本動物学会第89回札幌大会, Sep. 2018, Japanese, 札幌, Domestic conference

  Poster presentation


• Honeybees choose their way to home using e-vector information from the sky

  Sakura M, Onishi H, Okuyama A, Matoba N, Kobayashi N, Okada R

  International Congress for Neuroethology 2018, Jul. 2018, English, Brisbane, Australia, International conference

  Poster presentation


• 集合フェロモン濃度変化がカシノナガキクイムシ飛翔特性に及ぼす影響

  石野 貴大, 岡田 龍一, 伊東 康人, Long Duy Pham, 山崎 理正, 池野 英利

  日本森林学会, 2018, Japanese, Domestic conference

  Oral presentation


• ダンス追従バチの巣内でのふるまい、ミツバチシンポジウム

  岡田 龍一

  ミツバチシンポジウム, 2018, Japanese, Domestic conference

  [Invited]

  Invited oral presentation


• Behavioral responses of the ambrosia beetle Platypus quercivorus to chemical volatiles from host leaves

  PHAM Duy Long, YAMASAKI Masamichi, ITO Yasuto, OKADA Ryuichi, IKENO Hidetoshi

  日本森林学会, 2018, English, Domestic conference

  Oral presentation


• Place memory based on visual information in the cricket Gryllus bimaculatus

  MATSUBARA Nobuaki, OKADA Ryuichi, SAKURA Midori

  日本比較生理生化学会第39回福岡大会, Nov. 2017, English, 福岡大学, Domestic conference

  Poster presentation


• 数理モデルを用いたミツバチコロニーサイズの成長と縮小特性の再現

  甘中 健一, 岡田 龍一, 池野 英利, 木村 敏文, 大橋 瑞江

  日本生態学会, 2017, Japanese, Domestic conference

  Oral presentation


• 集合フェロモンによってカシノナガキクイムシの飛翔特性に違いが生じるか？

  奥田 直人, 岡田 龍一, PHAM Duy Long, 伊東 康人, 山崎 理正, 池野 英利

  日本森林学会, 2017, Japanese, Domestic conference

  Oral presentation


• ミツバチは天空のeベクトル情報に基づいて飛行方向を決定する

  SAKURA MIDORI, 奥山 晶子, 的場 なつみ, 小林 宜弘, 岡田 龍一

  日本動物学会, 2017, Japanese, Domestic conference

  Oral presentation


• ミツバチの尻振りダンスにかくされた餌集めの工夫

  岡田 龍一

  ミツバチ科学研究会, 2017, Japanese, Domestic conference

  [Invited]

  Invited oral presentation


• ミツバチコロニーのエネルギー収支の見積もり-成長期と退行期の比較

  吉田 澪, 大橋 瑞江, 木村 敏文, 岡田 龍一, 池野 英利

  日本生態学会, 2017, Japanese, Domestic conference

  Oral presentation


• ニホンミツバチにおける女王パイピング（トゥーティング、クワッキング）の特徴および分蜂との関係

  山本 哲, 菅原 道夫, 池野 英利, 岡田 龍一

  日本動物学会, 2017, Japanese, Domestic conference

  Oral presentation


• ダンス追従バチは複数のダンス蜂を追従する

  岡田 龍一, 池野 英利, 青沼 仁志

  日本動物学会, 2017, Japanese, Domestic conference

  Oral presentation


• Place memory based on visual information in the cricket Gryllus bimaculatus

  MATSUBARA Nobuaki, OKADA Ryuichi, SAKURA Midori

  日本比較生理学会, 2017, Japanese, Domestic conference

  Poster presentation


• Behavior of follower bees in a hive before departure after the dance communication

  OKADA Ryuichi, IKENO Hidetoshi, AONUMA Hitoshi

  日本比較生理学会, 2017, Japanese, Domestic conference

  Poster presentation


• ミツバチの採餌行動におけるエネルギー収支

  澤井 穂高, 岡田 龍一, 吉田 澪, 大橋 瑞江, 木村 敏文, 池野 英利

  日本生態学会, 2016, Japanese, Domestic conference

  Poster presentation


• ミツバチのコミュニケーション：個体の振るまい、コロニーの振るまい

  岡田 龍一

  ミツバチシンポジウム, 2016, Japanese, Domestic conference

  [Invited]

  Invited oral presentation


• カシノナガキクイムシの飛翔能力は何によって決まるのか

  深谷 智史, 奥田 直人, 岡田 龍一, 伊東 康人, 池野 英利, 山崎 理正

  日本森林学会, 2016, Japanese, Domestic conference

  Oral presentation


• Seasonal changes of energy gain and consumption in a honeybee colony

  YOSHIDA Mio, OHASHI Mizue, KIMURA Toshifumi, OKADA Ryuichi, IKENO Hidetoshi

  日本生態学会, 2016, English, Domestic conference

  Oral presentation


• Phototaxis behavior of ambrosia beetl Platypus quercivorus before and after flight

  PHAM Duy Long, YAMASAKI Masamichi, ITO Yasuto, OKADA Ryuichi, IKENO Hidetoshi

  日本生態学会, 2016, English, Domestic conference

  Oral presentation


• Optimal selection of honeybee waggle dance types for colony survival

  OKADA Ryuichi, IKENO Hidetoshi, SAKAE Misa, IIZUKA S, KIMURA Toshifumi, OHASHI Mizue

  日本比較生理学会, 2016, Japanese, Domestic conference

  Poster presentation


• Improvement in processing time of the tracking software, K-Track

  KIMURA Toshifumi, OHASHI Mizue, OKADA Ryuichi, IKENO Hidetoshi

  日本比較生理学会, 2016, Japanese, Domestic conference

  Poster presentation


• Honeybees choose their way to home using e-vector information from the sky

  SAKURA Midori, OKUYAMA Akiko, MATOBA Natsumi, KOBAYASHI Norihiro, OKADA Ryuichi

  日本比較生理学会, 2016, Japanese, Domestic conference

  Poster presentation


• Behavioral pattern of a follower bee in the dance communication

  OKADA Ryuichi, AONUMA Hitoshi, IKENO Hidetoshi

  The 22nd International Congress of Zoology, 2016, English, International conference

  Poster presentation


• ミツバチコロニーにおける採餌活動の日的変化および季節的変化の解析

  吉田 澪, 大橋 瑞江, 木村 敏文, 岡田 龍一, 池野 英利

  日本生態学会, 2015, Japanese, Domestic conference

  Oral presentation


• フライトミルを用いたカシノナガキクイムシの飛翔能力の測定

  深谷 智史, 岡田 龍一, 伊東 康人, 池野 英利

  日本森林学会, 2015, Japanese, Domestic conference

  Oral presentation


• ニホンミツバチにおける音コミュニケーション

  山本 哲, 菅原 道夫, 岡田 龍一, 池野 英利

  日本動物学会, 2015, Japanese, Domestic conference

  Oral presentation


• セイヨウミツバチの採餌経験に基づく偏光定位行動の解析

  SAKURA MIDORI, 的場 なつみ, 小林 宜弘, 岡田 龍一

  日本動物学会, 2015, Japanese, Domestic conference

  Oral presentation


• コンピュータシミュレーションによるミツバチのコロニーの生存戦略の解析

  岡田 龍一, 栄 美紗, 木村 敏文, 大橋 瑞江, 池野 英利

  日本動物学会, 2015, Japanese, Domestic conference

  Oral presentation


• Detection of bees’ trajectories in the backward movie using a tracking software, K-Track

  KIMURA Toshifumi, OHASHI Mizue, CRAILSHEIM Karl, SCHMICKL Thomas, OKADA Ryuichi, IKENO Hidetoshi

  Comp Biol 2015 （日本比較生理学会・日本内分泌学会合同大会, 2015, Japanese, Domestic conference

  Poster presentation


• Behavioral pattern of a follower bee during the honeybee dance communication

  OKADA Ryuichi, IKENO Hidetoshi, KIMURA Toshifumi, OHASHI Mizue, AONUMA Hitoshi, ITO Etsuro

  Comp Biol 2015 （日本比較生理学会・日本内分泌学会合同大会, 2015, Japanese, Domestic conference

  Poster presentation


• ミツバチコロニーの生存維持における８の字ダンスの効果

  岡田 龍一, 栄 美紗, 木村 敏文, 大橋 瑞江, 池野 英利

  日本動物学会, 2014, Japanese, Domestic conference

  Oral presentation


• マルチモーダル刺激における衝突回避および飛行安定行動の解析

  東條 美紀, 長谷川 雄二, 岡田 龍一, 池野 英利

  日本動物学会, 2014, Japanese, Domestic conference

  Oral presentation


• ニホンミツバチとセイヨウミツバチにおけるキンリョウヘンの匂いに対する感覚応答と学習効果

  原田 礼花, SAKURA MIDORI, 藍 浩之, 菅原 道夫, 岡田 龍一

  日本動物学会, 2014, Japanese, Domestic conference

  Oral presentation


• Spiking activity of an identified mushroom body extrinsic neuron during olfactory memory acquisition in the honeybee

  OKADA Ryuichi, MENZEL Randolf

  The 11th International Congress of Neuroethology, 2014, English, International conference

  Poster presentation


• Sensory responses to the oriental orchid odors in the Japanese and European honeybees

  HARADA Ayaka, AI Hiroyuki, SUGAHARA Michio, OKADA Ryuichi, SAKURA Midori

  The 11th International Congress of Neuroethology, 2014, English, International conference

  Poster presentation


• Orientation to the polarized light in flying honeybees

  SAKURA Midori, KOBAYASHI Norihiro, OKADA Ryuichi

  The 11th International Congress of Neuroethology, 2014, English, International conference

  Poster presentation


• Olfactory learning-related plasticity of the mushroom body neurons in the honeybee

  OKADA Ryuichi, MENZEL Randolf

  Hokkaido Neuroethology Workshops 2014, 2014, English, International conference

  [Invited]

  Invited oral presentation


• Improving tracking accuracy of the software to track multiple honey bees, K-Track

  KIMURA Toshifumi, OHASHI Mizue, CRAILSHEIM Karl, SCHMICKL Thomas, OKADA Ryuichi, RADSPIELER Gerald, IKENO Hidetoshi

  The 11th International Congress of Neuroethology, 2014, English, International conference

  Poster presentation


• 飛行中のミツバチの偏光定位行動

  SAKURA MIDORI, 小林 宜弘, 岡田 龍一

  日本動物学会, 2013, Japanese, Domestic conference

  Oral presentation


• 誤差情報を含んだ８の字ダンスによるミツバチの適応的採餌行動

  岡田 龍一

  無脊椎動物神経生物研究会, 2013, Japanese, Domestic conference

  Oral presentation


• 蛍光相関分光法を用いたグルコースの高感度測定

  伊藤 悦朗, 森川 美佳, 児玉 裕美, 岡田 龍一, 渡部 聡, 三浦 敏明

  日本薬学会, 2013, Japanese, Domestic conference

  Oral presentation


• ミツバチが匂いを記憶している時の脳の活動

  岡田 龍一

  ミツバチミニシンポジウム, 2013, Japanese, Domestic conference

  [Invited]

  Invited oral presentation


• Orientation to the polarized light in flying honeybees

  SAKURA Midori, KOBAYASHI Norihiro, OKADA Ryuichi

  International Conference on Invertebrate Vision, 2013, English, International conference

  Poster presentation


• Development of a tracking program, K-Track, for analyzing honeybee’s behaviors

  KIMURA Toshifumi, OHASHI Mizue, CRAILSHEIM Karl, SCHMICKL Thomas, OKADA Ryuichi, RADSPIELER Gerald, IKENO Hidetoshi

  日本比較生理学会, 2013, Japanese, Domestic conference

  Poster presentation


• Consolidation of long-term memory by molluscan insulin-related peptide in Lymnaea

  ITO Etsuro, OKADA Ryuichi, HATAKEYAMA Dai, OTSUKA Emi, OKUTA Akiko

  日本比較生理学会, 2013, Japanese, Domestic conference

  Poster presentation


• ミツバチのダンスはどんな効果があるのか？

  岡田 龍一

  ミニシンポジウム：ミツバチの行動と社会性, 2012, Japanese, Domestic conference

  [Invited]

  Invited oral presentation


• ダンス行動によるミツバチコロニーの環境適応：コンピュータシミュレーションによる解析

  岡田 龍一

  日本動物学会, 2012, Japanese, Domestic conference

  [Invited]

  Invited oral presentation


• Neural network involved in olfactory learning in the honeybee brain

  OKADA Ryuichi

  日本神経科学会, 2012, English, Domestic conference

  [Invited]

  Invited oral presentation


• 数理モデルをもちいた８の字ダンスによるミツバチの適応的採餌行動の解析

  岡田 龍一

  自律分散システムシンポジウム, 2011, Japanese, Domestic conference

  [Invited]

  Invited oral presentation


• ミツバチにおける８の字ダンスによる情報伝達とその効果

  岡田 龍一

  Animal2011（日本動物心理学会、日本動物行動学会、応用動物行動学会、日本家畜管理学会合同大会）, 2011, Japanese, Domestic conference

  [Invited]

  Invited oral presentation


• ８の字ダンスによるミツバチコロニーの採餌戦略

  岡田 龍一

  日本進化学会, 2008, Japanese, Domestic conference

  [Invited]

  Invited oral presentation


• Foraging strategy of the honeybee colony by waggle dance

  OKADA Ryuichi

  International Seminar on Current Issues in Social Insect Research -In Case of Honeybee and Ants, 2008, English, International conference

  [Invited]

  Invited oral presentation


• 昆虫のシンボリック言語

  岡田 龍一

  日本機械学会, 2007, Japanese, Domestic conference

  [Invited]

  Invited oral presentation


• ミツバチの餌と匂いの連合学習によるキノコ体出力ニューロンの可塑性

  岡田 龍一

  ミツバチとショウジョウバエの比較分子神経生物学～脳と行動進化を遺伝子レベルで捉えなおす～, 2007, Japanese, Domestic conference

  [Invited]

  Invited oral presentation


• 運動制御における昆虫の脳の基本設計

  岡田 龍一

  日本比較生理生化学会, 2006, Japanese, Domestic conference

  [Invited]

  Invited oral presentation


• ミツバチのにおい学習と埋め込みワイヤ電極

  岡田 龍一

  日本動物学会, 2006, Japanese, Domestic conference

  [Invited]

  Invited oral presentation


• ショウジョウバエ触角葉内のGABA介在性神経連絡

  岡田 龍一

  日本味と匂学会セミナー, 2005, Japanese, Domestic conference

  [Invited]

  Invited oral presentation


• GABA-mediated neural connections in the Drosophila antennal lobe

  OKADA Ryuichi

  日本比較生理生化学会, 2005, English, Domestic conference

  [Invited]

  Invited oral presentation


• 昆虫のキノコ体の慢性記録と運動制御における脳の基本設計

  岡田 龍一

  COE昆虫科学セミナー, 2004, Japanese, Domestic conference

  [Invited]

  Invited oral presentation


• Implications for the basic organization for motor control in the cockroach brain

  OKADA Ryuichi

  Japanese-French Postdoc Meeting on Insect Neuroethology, 2004, English, International conference

  [Invited]

  Invited oral presentation

• 昆虫ナビゲーションにおける偏光コンパスの概日時計に基づく時間補償機構

  佐倉 緑, 藍 浩之, 岡田 龍一, 志垣 俊介, 渕側 太郎

  日本学術振興会, 科学研究費助成事業, 基盤研究(B), 神戸大学, 01 Apr. 2022 - 31 Mar. 2027


• ミツバチのベクトル統合の神経回路と蜜源ナビゲーションにおける制御機構の解明

  藍 浩之, 岡田 龍一, 佐倉 緑, 池野 英利

  日本学術振興会, 科学研究費助成事業, 基盤研究(C), 福岡大学, 01 Apr. 2022 - 31 Mar. 2026


• ミツバチのナビゲーション行動を成熟させる神経メカニズムの解明

  岡田 龍一

  日本学術振興会, 科学研究費助成事業, 基盤研究(C), 神戸大学, 01 Apr. 2022 - 31 Mar. 2025


• Error avoidance strategy of Platypus quercivorus on their host selection process

  山崎 理正, 伊東 康人, 岡田 龍一, 池野 英利, 森 直樹, 西岡 正恵

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), Kyoto University, 01 Apr. 2021 - 31 Mar. 2024


• ミツバチのナビゲーションにおける方向と距離の情報統合の脳内メカニズム

  岡田 龍一

  日本学術振興会, 科学研究費助成事業, 基盤研究(C), 神戸大学, 01 Apr. 2019 - 31 Mar. 2023

  巣や餌場などの目的地へ移動する「ナビゲーション行動」では、移動中に方向情報と距離情報を逐次取得しそれらを統合して移動を完遂するが、脳内での統合の仕組みについてはほとんどわかっていない。そこで、本研究ではトンネルを用いて採餌訓練をさせたミツバチをバーチャルリアリティ空間内で疑似的に採餌のナビゲーション飛行を再現させ、その時の脳内のナビゲーション中枢の神経活動を記録し、どのように方向情報と距離情報が脳内で統合されるかを明らかにすることを目的としている。 今年度は、昨年度の組織化学的研究で得られた知見を利用して、トンネル内で採餌訓練したミツバチの電気生理実験を行う予定であったが、新型コロナウイルスの影響等からトンネルでの採餌訓練の実施に支障がでた。そのため急遽学内で実施可能な場所を検討し、代替場所にトンネルを設置した。しかし、代替場所で採餌訓練を行ったものの期待したような訓練効果を得ることはできず、時間の浪費を避けるために学内スペースでの採餌訓練を断念した。 その一方で、ミツバチが方向情報を得るために利用している偏光を検出する複眼背側部（DRA）の光に対する応答の記録を行ったところ、DRAは紫外領域の光に特に強く応答をすることがわかった。さらに興味深いことに、この神経応答は記録した時刻によって応答強度が変化した。このことは、ミツバチの偏光情報処理機構に何らかの時間補償機構があることを示唆しており、自然状態でのミツバチの採餌行動の性質を考えると、ナビゲーションの成功の保証を与えている可能性が高い。 現在は、今年度実施できなかった、従来の場所でのトンネル実験の再開と訓練したミツバチでの電気生理実験の準備を進めている。


• Mechanism for detecting the azimuth encoded in the honeybee waggle dance

  AI Hiroyuki

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), Fukuoka University, 01 Apr. 2018 - 31 Mar. 2022

  The honeybee waggle dance followers orientate to the dancer not by vision but the antenna, for detecting the azimuth encoded in the dance. On this study we investigated whether both antennae are necessary for the orientation, and what region on the antenna is critical for the orientation by analyzing the waggle dance follower of which local regions of either antenna was covered by a resin on newly emerged adults. As the results we found local coverings of either tip of flagella, middle of flagella or pedicel of one antennae completely defect the orientation to both sides of waggle dancer. These results suggest that the followers orientate the dancer by detecting the difference between somewhat bilateral antennal inputs for deciphering the azimuth.


• Identification of primary attractants for Platypus quercivorus and their application to the control of Japanese oak wilt

  Yamasaki Michimasa

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), Kyoto University, 01 Apr. 2018 - 31 Mar. 2021

  The ambrosia beetle Platypus quercivorus causes mass mortality of oak trees, Japanese oak wilt, by transporting a pathogenic fungus from trees to trees. Using a flight mill to simulate insect flight in a room, we showed that there are sexual differences in the flight ecology of the beetle, and elucidated the causes of the large variation in its flight distance. Two-choice tests of host and non-host tree saplings showed that the beetle is attracted to volatiles from the canopy of host trees and avoid volatiles from the canopy of non-host trees. It was clarified that the beetle bores into narrow-angled crevices regardless of the type of wood, and that this behavior is activated after flight. Long-term forest dynamics studies in natural and secondary forests clearly showed the effects of Japanese oak wilt, including a decrease in species diversity.


• Neural mechanism of the time compensation for the detection of a navigating direction using the polarized light in the honeybee

  Okada Ryuichi

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), 01 Apr. 2016 - 31 Mar. 2019

  The central complex is a crucial area in the insect brain for navigation using polarized light. Electrophysiology from the central complex exhibited that some central complex neurons responded to polarized light with a specific e-vector preference. Immunohistochemistry in the central complex was performed against iono- and metabotropic GABA receptors, and showed a different distribution between the two types of receptors. Strong positive signals for the ionotropic GABA receptor were found in the central complex while very few and fair signals were found for the metabotropic GABA receptor. This strongly suggests that ionotropic GABA receptor is dominant for information processing in the central complex compared to metabotropic receptor.


• Dinamical neuronal modeling of insect navigation based on polarization vision

  SAKURA MIDORI, HENZE Miriam J.

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), Kobe University, 10 Jul. 2015 - 31 Mar. 2018

  It is well known that many insects deduce their heading direction using polarized skylight. However, it is still unclear how the polarized skylight information, which forms complicate pattern in the sky and even heavily depending on solar azimuths and/or weather conditions, is coded by neural networks in the brain. In this study, we tried to clarify this by dynamical neural modeling using biological and astronomical data. We first analyzed input manners of the polarized light information by a sensor map constructing from the morphological data of the polarized light-detecting area of the compound eye (DRA). Moreover, we tested the accuracy in orientation outputs of the neural network model constructed by the response properties of polarization-sensitive neurons in the brain.


• Brain mechanism

  Okada Ryuichi

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), 01 Apr. 2013 - 31 Mar. 2016

  To examine neural mechanisms underlying memory formation, the activities of a mushroom body output neuron, PE1 neuron, was analyzed because this neuron shows a learning-related plasticity. However, it is still unknown whether and when PE1 changes its responses during the acquisition period. Using chronic recording from PE1 of a learning bee, we analyzed the spontaneous activity of PE1 between acquisition trials. The spectrum analysis for spontaneous activity showed that the peak of power spectrum of PE1 was shifted to the lower frequency along acquisition trials, suggesting that the inhibition of PE1 spiking activity became stronger than before learning. Next, to reveal inhibitory synaptic connections about PE1, we performed immuno-staining against GABA, iono-, and metabotropic GABA receptors. Immunohistology suggested that PE1 has no GABA-receptors, and thus an indirect neural control might be dominant in an inhibitory connection to PE1.


• Behavioral and electrophysiological study of insect polarization vision by simultaneous recording of polarotactic behavior and brain neural activities.

  Sakura Midori, OKADA Ryuichi

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), Kobe University, 01 Apr. 2013 - 31 Mar. 2016

  Many insects use polarization pattern of the sky for orientation and navigation. Honeybees show clear polarotaxis to a certain e-vector orientation. In this study, polarotactic behavior of the bee trained to visit an artificial feeder was analyzed. The bees caught at the feeder oriented to the e-vector they experienced during their foraging flight, indicating that they utilized polarized light information from the sky to memorize the food location and to adjust their flight direction. In addition, an extracellular recording method from polarization-sensitive neurons in the bee brain was developed, which allows us to monitor neural responses of a flying tethered bee brain in a flight simulator.


• Effect of social behaviour on carbon budget of honeybee colony under climate change

  MIZUE Ohashi, IKENO Hidetoshi, KIMURA Toshifumi, OKADA Ryuichi, NAKAGIRI Nariyuki

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Challenging Exploratory Research, University of Hyogo, 01 Apr. 2012 - 31 Mar. 2015

  Honeybee keeps their colony under dramatic change of environment by using social behavior. This study aimed to evaluate honeybee adaptation to environment by measuring energy budget of the hive. The energy budget was estimated from inflow and outflow of carbon from the hive. We found clear daily change of carbon inflow, increasing in evening in summer and increasing noon in autumn. It also decreased from summer to autumn. Total amount of carbon inflow during 3 months was 2.4 kg. Carbon outflow decreased linearly with the decrease of temperature, increasing from summer to autumn. Total amount of the outflow was 0.82 kg.


• Neural mechanisms of motivation-dependent learning and memory

  OKADA Ryuichi

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), Tokushima Bunri University, 2010 - 2012

  To clarify neurophysiologically how motivation influences the efficiency of the learning and memory, I recorded the activities of the brain neurons from honeybees under training for olfactory learning. I have been progressively analyzing data at the level of the neural circuit. With executing experiments, I successfully recorded brain activities in the entire process when olfactory memory is forming. One of honeybee brain neurons, PE1, is known to reduce the responses to learned odor after the memory was absolutely consolidated. I found that the voluntary activity of the PE1 decreased just before forming memory and the first reduction of the odor response was taken place just after the memory was formed, not when the memory was formed..


• 社会性適応のための行動変容機構の研究

  伊藤 悦朗, 池野 英利, 木村 敏文, 岡田 龍一, 大橋 瑞江

  日本学術振興会, 科学研究費助成事業, 特定領域研究, 徳島文理大学, 2008 - 2009

  花から巣に戻ったミツバチは訪れた花の位置(情報)を、「8の字ダンス」という特異的な行動によって巣内のミツバチに伝える。このようなミツバチの社会性の研究は生物学だけからのアプローチでは解明が難しく、工学系研究者との共同研究によって8の字ダンスに挑戦すれば、必ずや世界に先駆けてそのメカニズムを明らかにできると考え、本研究を進めてきた。われわれはミツバチの社会性適応行動を例に取り、特にその中でも他者とのコミュニケーション手段である「8の字ダンス」の基本機序をシステムとして理解を深めながら、社会性適応のための行動変容機構を明らかにすることが本研究課題の目的である。これまで生物データの取得のためにミツバチのダンス行動をビデオ撮影してきた。解析の結果、巣内ミツバチの歩行パターンと1秒あたりの最大移動距離、ダンスの発生場所の分布、ダンス情報の性質、追従バチの追従パターンなど、モデル構築に必要な多くのパラメータを取得した。そこで今年度はこれらのパラメータを利用して、ミツバチの採餌行動のマルコフモデルを構築後、シミュレーション実験を行った。その結果、われわれのモデルはミツバチの採餌行動をよく表現できていること、ダンスによる情報伝達は採餌の効率をあげていることなどがわかった。これらと平行して、ミツバチの行動は巣内外の環境に柔軟に適応して調節されるので巣内外の環境を自動で経時的に計測するためのシステムも同時に構築した。また、効率よく行動パラメータを取得するために、ベクトル量子化法を用いた、ミツバチの自動追跡システムを開発した。これらのことから得られる結果を組み合わせることで、ダンス行動によるコロニー維持の効果や情報の伝搬様式などのより深い理解につながると期待される。